You could find what you needed info-wise at this guys site:
1988 Monte Carlo LS1 Swap
He's got a similar configuration to your car and has completed the swap. Now running 12's and getting 428/400 HP/TQ to the rear wheels. Holy crap!
He has a lovely "Swap cost data" sheet outlining the money spent to swap the stock engine and tranny in PROPERLY. Much was custom. He finished just short of $10,000.
I've seen swap mounts offered for other body styles. around $200 You can figure you'll have $6-7000 in the engine and tranny alone.
It would be a neat swap but you will pay for it. If you are looking for performance for dollar ratio, a 455 Pontiac with a custom MPI intake will be WAY cheaper, and easier. Make more power and be more exotic.
The LS1 cannot make up for the price difference in MPG. ever. Weight difference is not worth worrying over after you put E-heads on a traditional Poncho. A 6 speed tranny costs the same for either setup. I can't find any real sellable benefit to the LS1 swap, other than to do it, be different, bragging right, or novelty. I think LS1 are respectable and an LS1 swap very cool, but for now not quite worth it.
As much as I hate to be the one to point this out I will. On the Chevy/Corporate arguement about the LS1, the LS1 in my opinion is a corporate engine belonging to all GM marks. BUT... the LS1 does have a CHEVY bellhousing pattern.
Compelling evidence that it is a Chevy engine.
Maybe because it's the only V8 pattern they have now? dunno. The Caddy Northstar doesn't use a Chevy bellhousing pattern.
Cringe
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1968 Firebird Coupe
350 HO
TH350
3.23's
PS, PDB and Deluxe interior
GPE Starter MSD billet
Rodney Red Rad MSD 6a
Currently apart for suspension upgrades.