Have you priced up all the extra stuff you'll need to put a t series in compared to just bolting in a 5k? I'm guessing a 5k just bolts straight up? Keep same gearbox. Compared to new mounts for engine, gearbox, custom driveshaft (unless there is bolt in option), wiring up on sensors for water temp, tacho etc.
Just sounds like a shed load of hassle for no gain. Can you do it all yourself or?
If you can't afford to buy a 5k outright I just don't like your chances of finishing the 3t transplant.