need advice on an engine swap Options

[Zimluura]

My car's been leaking trace amounts of oil for a while now. I recently I had an overheating incident on the highway. got towed to wall-mart and put a gallon of coolant in and was able to drive home.
Just got the diagnosis from my mechanic and he says the coolant system isn't leaking, but there's a large amount of pressure building in it. [edit] he thinkgs it's a cracked head gasket [edit]. I think he said he stopped it at 27psi. just put 5k into getting an auto to manual conversion too.

so I think i've got to do an engine swap now. the question is, what should it be? my primary mechanic doesn't like to veer off the beaten path, mostly because he doesn't like to go over estimates. so he says he can ge a reman 5s-fe for 3.5K and then he estimates perhaps as high as another 3.5K for the labor and extra parts if he needs any. he says he has no idea on how much a rebuild would be, let alone rebuilding with better parts - which are hard to find and, for 6gc, usually expensive.

the mechanic who did my manual conversion, he lives too far away to by my primary, but he doesn't mind trying swaps and things like manual conversions. and his work seems pretty good, in-so-far that my primary mechanic said the conversion looked like it was well done.

for a while now i've been thinking about the 2gr-fe. if they can fit it in an mr2 it can probably fit in a celica. but i'd also be, as far as i can tell the first to try this swap. i'm not a complete idiot when it comes to cars, but i don't have a garage, and that really limits my ability to further educate myself.

what do you guys think i should do?
I'm prioritizing 100% legal with an egr system & OBD2 (car is a '99), i'd like good reliability and i'd like a bit more power, i'd like to keep the s54 transmission because it was rebuild less than a year ago (until i'm ready to do the oft-spoken, seldom-done e154f).

so far here are the options i'm considering:
* 2GR-FE swap, (heard the e154f won't like v6, but i think a custom rear manifold might clear the xfer case - but it's a bridge i can look at crossing when i'm ready for awd conv), is it feasible to stick with the s54? there are certainly times when i want more power than the 130 i have, but i generally don't push the engine.

* 1MZ-FE seems popular - seems a safer choice because it's been done before.

* get current 5S-FE rebuilt with better internals parts mostly favoring durability & slight performance improvement. any recommendations on where i would get those parts would be good then.

* build a garage & learn to rebuild the 5S-FE myself (most expensive option with least immediate payoff)

This post has been edited by Zimluura: Oct 4, 2012 - 2:45 PM