I just cracked a block, back of number 2 cylinder.  Not happy. About 400hp at crank, 22psi, stock head and manual NA cams.  0.20th (0.5mm) oversized forged pistons. 7500rpm limit.
Its a Gen 3 NA block (its in a RWD corolla, and all 3SGTE blocks are shaved to suit GT4 so not goood for RWD).
Sounds like it happens a lot with gen 3 blocks.
I have another gen 3 NA block that has teh reinforced No1 cylinder (behind water pump), didnt know that was available in gen 3. 
I also have a FWD beams motor (grey top) with reinforced block.
I just bought a 1995 5SFE block and a 1998 x20 series camry block.  I will post pics of all the blocks soon.
The x20 block does look to have thicker cylinder walls if you look in the water gallery).
 

Yeah all this info is out there. Do a search on mr2oc.com for even more pictures and info.

5sfe doesnt have the silly water jacket between 2 and 3, which is one of the main issues with pre caldina/beams blocks.

Use a blacktop rwd beams for a rwd car. Much easier than adapting east/west motors. Blacktops are dirt cheap now too. I have one in my BMW.

Blacktop beams is not an easy conversion.  Need custom engine mounts, modify the intake manifold (brake booster in the way), Modify fuel rail for return line, and you get a sump that hits your sway bar.  Then there is the height issue and ECU issues, and it cant handle boost.  Also you have to use a Y bellhousing with it because the starter is on the drivers side
 
By using a NA block, I bolt on ST141 mounts, 5SFE oil and water pump, Spacia pickup, splash plate and sump, and weld up an intake manifold and water pipes and weld ST141 mounts to the crossmember (easy). I have a bunch of SA63 bellhousings and have done this conversion 3 times.  I also run Manual NA cams because they have much more duration then turbo cams.  The GT3071r is plenty big enough for a <250' cam motor (0.64 rear).  I found when I tried 268 cams the 0.86 rear was essential.  I run ~21psi daily, and the occational push to 25psi (maybe 28 by accident).  I had to run BRK8EIX to stop ignition problems above 22psi.
 
I am on my 5th gen 3 engine with this car tho :( but I do give it a hard time.
1. Forged, 40th Low Comp Arias pistons, spool rods.  Spun a big end after a month, and was running it NA! (Wrong pickup).
2. Same engine rebuilt with new crank - After a few months something sucked into the engine and scratched the bores and pistons.
3. Dead stock Caldina internals in a stock Gen 3 NA block - Got over a year out of it at ~22psi.  Took it to 25psi and broke a ring land.
4. SPS 20th pistons, spool rods - Cracked the cylinder at Willowbank after about 5 runs on my second week of racing. Still drove home.
5. SRP 86mm pistons, Late gen 3 reinforced block.  In car next week.
 
Good to hear that IDB is still around!  I bought 2TG valves and gears from you in the early 90s :)
 
 

Late gen3 will have reinforcing around water pump but your still going to crack it in the bores by the sounds of your setup.

Highly recommend just going straight to the 5s block.

Do you have any spareoof the gen3 na Cams? What were the motors originally in?

I have a black top with a loom and ECU, but it is easier to fit a gen3 then it is to fit a black top (Mounts, intake manifold, sump issues and height to name a few).

OK I just examined 4 blocks, and it seams that not all reinfoced 5SFE blocks have the same cylinder wall thickness.
Gen 3 block - 7mm minus aprox 1.5mm (it recesses about 10mm down).
Noah (Spacia) 3SFE block - 7.5mm minus aprox 1.5mm (it recesses about 10mm down). NOTE has oil squirter blocks
1996 Celica 5SFE - 7mm with slight recess 12mm down.  No oil squirter blocks, no balance shafts (Same crank as camry 5S but no gear pressed on).
1998 Camry x20 5SFE - 8mm with slight recess 15mm down.  No oil squirter blocks.  Oil feed for balance shafts.

All of these blocks cept Gen 3 has the external reinforcement near water pump.
That crack of mine starts at the recess area :(
 
No spare cams.  All NA Gen3 have 250' intake.  Manuals have 250' exhaust as well.  I am running 2 intake cams.  Motors are from Caldina and MR2
 

according to my specs, only the manual gen3 has the 252 9.8 intake cam.  auto gen3 GE's got turbo inlet cams for inlet and exh, but exh is slightly lower lift (240/8.7-8,2mm)
 
the red/greytop beams exh cam is usable in the gen3 for an exh cam with some adjustments to timing for the correct lobe centres, but it's not quite as good as the gen3 NA intake. it's only 244/9.2
 
5s block doesn't have cast water jackets around the bores 2/3. they're solid with drilled/bored water galleries. more common for blocks to crack in the bores than around the water pump.
 
AFAIK no 3s blocks have 5s block strength in the bores.

ok too many pics for here so I put them on tumblr

ke70.tumblr
 
And your specs are wrong!
Turbo cams and NA exhaust cam -88362
NA intake -88460

I have a Gen 3 caldina GT-T head and 2 x Caldina NA Gen3 heads and a MR2 Gen 3 head.  All have -88362 exhaust, and all NA heads I have use -88460 intake.  The grey top exhaust has huge lift but much bigger base circle so shims would have to be reduced a lot! Also no dissy drive on a beams cam.
 

Ok just measured:- (and the EPC is wrong too!)
-88362 has 32.5 base, 9mm lift
-88460 has 32.5 base, 10.2mm lift
Grey top intake -88560 34.5 base, 10.5 lift
Grey top exhaust -88460! 32.6 base, 9.2 lift (ok wtf with the part number?)
Cant be bothered measuring my black top cams.