You don't...
A 350 CID w/2bbl carb will get you the best mileage and power.
Probably. 9 years ago, I put a new 350 crate engine into my 1979 El Camino, which was originally equipped with a 305. Bolted in and re-used all ancillary components, including carb and intake. Still running.
You can put Oldsmobile 350 heads on an Oldsmobile 307, if the 307 is 1984 or older. It will take some work but it can be done, I know for a fact that it can, because my 307 has 350 heads on it. It runs great. I'm not sure about the cam though.
You probably need to be a bit more specific. I've got a 1972 El Camino with a 350 engine in it. I get about 17 mpg now that I just put new spark plugs and wires in it.
Yes. You'd need to find a v8 donor car to transfer the emissions equipment, etc.
Yes. Unless you put in a modifyed cam.
both good engines but i have 65 elcamio with a 454 and it is just the best engine i have ever put into a chev. i would go with a 454
You can put the Vortec in it if you have the wiring and ecm to run it. or you could use the Vortec heads and an aftermarket intake and really wake up your engine. The vortecs use a roller cam.
Yes. Contact the cam manufacturer of your choice for a recommendation.
MPI's usually have electric fuel pumps to put out the pressure needed. so no lobe.
An olds 350 engine such as one that they put in the 1979 toronados. Don't think you could put a Chevy 350 in without major mods.
Can you? Yes, any engine swap is possible if you have enough money. My question is why? Just get a twin turbo, a good cam and reset your EFI