You say that you are still making payments on the car. The last thing in the world you should do right now is start making changes on the powertrain.
What happens if things so south in a hurry; and believe me they can and do. You’re sitting there with an inoperative vehicle that you still owe money on.
Making payments on something you can’t use is very distasteful. If you fail to keep making payments on a now unusable vehicle it will be repossessed. The lender will sell it for peanuts and come after you for the remaining balance.
IN the meantime- perhaps check junkyards for a parts car or two that have the configuration you are looking for- a 91 or so with a 5.7L. That may prove to actually be a more doable project.
My advice would be to echo @VOLVO_V70. Get the engine you have now in decent shape, then sell the car, and buy what you want. You’ll save a lot of money and hassle. The only time I did an engine swap was when I had two CRXs, and transplanted engines between them to make the non-rusty car the one with the more powerful engine. And even that led to problems, even though both engines were a direct swap with almost no fuss.
Otherwise, the only time an engine swap makes sense is when you really like the car you have, but you want it to be a lot faster and there wasn’t a faster variant sold. So, if you really like the Honda Accord but want a 500hp motor in it, you’ve gotta do a swap because they didn’t sell one like that.
In your case, if you just particularly love the '91 Camaro and want a bigger engine in it, ditch the RS and get a Z28. It’ll be cheaper, easier, and much less problematic down the road.
Save your money for the time being and do it correctly. I’d skip the whole 350 Vortec. And go straight to the LS. At the local Cars and Coffee there’s a couple 3rd gen F-bodies with LS1/LS2 and even LS7 swaps. I’m fairly certain they make purpose-build swap kits for this.
