I've pretty much decided to do an LT1 with upgraded stuff but i'd like to know what other option there are out there....i want low 13 seconds with no nitrous (will use that later on for a maybe 12 second slip), gotta be fairly inexpensive (less than 4500 for it all), and gotta get fairly good MPG...and i gotta pass MA emmissions

LT1 or LS1 are your best options.

i agree: i wish i had thought of those limit when i built my engine. now i cant pass emissions and the car is basically useless untill i figure out a way to make it pass
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350 .040 over = 356
port polished and shaved aluminum heads (off 90 vette)
forged rods, crank, and pistons
10.8:1 total compression
crane cams 502/512 lift 284 duration
rpm performer manifold---rochester q-jet atop
stock distributor with 55k volt coil
headman headers 1 5/8 in primary w/ 3in collectors. 3in downpipe
dynomax catback exhaust, catco high flow cat

CANNOT PASS EMISSIONS

What kind of mods do you need to do to an LT1 to achieve this?

Well, from what I have heard you don't have to do hardly any mods to reach 13 seconds or even 12 seconds for that matter. You pretty much only need a cam headers and a chip and you can reach those goals. Doing some head work would also help out a bunch.

I'd do the LS1 for more fuel economy. Plus it's all aluminum so it would get you into the 12's almost bone stock as long as you can hook up, less weight on the front end. I have heard of people doing this swap and a little engine tuning, lots of suspension work, and they hit low 11's on a perfectly streetable car....... Not to mention you can get an entire LS1 and T56 combo for about 3000-3500 bucks (if not cheaper) if you look in the right place. LT1's I think are getting low 13's and 12's bone stock, dunno much about those for sure though. Just throw on the LT4 cam and some porting of the heads and that should be no problem with the LT1..
Good luck
Lc