Before you jump on a 'buy it now' - lol - You need to determine why you are upgrading and what purpose you use the mr2 to determine whats the best solution and the answer maybe a gen3 sump or moroso sump (more oil at sump) or even stay with a gen2 sump.
There are a combinations of solutions for gen2 3sgte block or late model 5s block and gen4/5 sump with gen 4/5 oil pump set up in regards to the oil cooler/filters;
Run the smaller n/a oil filter z386 at the stock position and run the larger z4xx turbo oil filter at the bottom location, or replacing the gen2 oil cooler with a gen3 oil cooler that has the block off plate on the oil cooler (custom HFHOE required), or running a late model 5s oil cooler (requires modification), or running a gen4/5 oil cooler (requires modification) at the stock gen2 position as it also has the cooler block off plate, or eliminating the stock gen2 oil filter position and running an external oil cooler.
The gen2 motor with gen2 sump can be upgraded by a late 90s model 5s oil pump upgrade that allows you to keep the gen2 sump, and is the cheapest upgrade for more oil flow at pump.
http://www.atsracing.com/Parts/Details/E-OILPUMP Google will provide further information or PM me and can share some pictures and info.