1988 Brougham engine question

My '88 Brougham has a 5.0L 307 olds in it, and the engine is not big enough for the car in my opinion, I mean come on, my caprice weighed less than this thing by a thousand pounds and even that had a 350.
Anyway, I was looking into a 350 with 350HP or possible a 383 stroker, since I could build it out and get around 400HP with budget mods.
I plan on keeping this Caddy, I bought it for $500 so if I drop another 4 grand in it, it's still a $4500 car.. it drives fine now, but I'm talking when the 307 poops out ( we don't know the mileage, somewhere either 103k or 203k.. it rolled over and the owner died so no one knows the actual mileage )
...Anyway.. I guess my question would be..
How difficult would it be to swap from an olds to a chevy 383 or 350? They sell mounting brackets don't they? Anyone done this before?
..Tell me what you think, 'cause this Caddy needs more HP then 140..