81mm bore builds have been successful by many many people. If you buy a 4T5 ,(idk how you would, 4T5s go for stupid money these days) make sure you pull all the rod caps and check for spun bearings. 4T5 doesn't have the magnesium coated bearings like the R and 2.3L engines have. More and more 4T5s have been found to have spun bearings. I would go ahead and swap in the mag. coated bearings.
A sleeved block would be very expensive. It depends on your budget. This also has its downfalls but hey, its your money 🤷♂️.
83mm bores (R engines mostly) crack their blocks; sometimes even on the stock tune. R's don't usually blow head gaskets unless you do something stupid like overheating it, etc.
That being said, I bought my R and 3/5 sleeves were cracked. I swapped in a 2.3L B5234T3/9 utilizing the R cylinder head and R oil pan.
Whatever you choose, take a really good lookover of the engine and make sure its a solid candidate. Last thing you want is a disaster scenario where you swap in a bad engine.
