The good news is that since you're going from a Pontiac 350 to a Pontiac 455 you can leave the cross member mounts right where they are. Also all your accessories will move over from the 350 to the 455 so no need to buy anything new.
That being said, GM put carbs on the 455 that flowed around 800cfm so that edelbrock carb of yours is going to choke the living heck out of that 455. What I'd recommend doing is sourcing a correct Quadrajet and then speak with Cliff Ruggles to get a rebuild kit that includes the goodies to get it running as it should.
Now as for beefing up the engine, the limit is your pocket book. What are you looking for performance wise out of the engine? Car? Are you looking for mostly a street car? Some track? Full on race? All these questions factor in to what parts you're going to be buying.
We can use my 455 as an example....
*1970 4 bolt main Pontiac 455 bored 60 over
*Stock crank
*Stock rods - I was on a budget and my car will not see track time
*New oversized flat top pistons
*New rings - sized for the overbore
*New bearings
*Custom ground cam - spec'd by R&R Engineering to 400hp (boo all you want, I didn't have a problem with him)
*Pontiac 6x-4 heads - hardened valve seats installed
*Comp Cams double roller timing chain
*Comp Cams 1.52 roller tip rockers
*Edelbrock Performer RPM intake manifold
*RA spec oil pump
*FlowKooler waterpump
*Pertronix Flamethrower HEI distributor
*IMI Hi-torque mini starter
*Holley 3310C carb - will be replaced with a quadrajet with the Cliff kit when I get the $$ for the kit
I'm also running a TH350 w/shift kit and 3.42:1 gearing w/posi out back. From a dead stop, I can spin my tires and the car for that matter. I've come out of a parking lot on more than one occasion, hit the gas to make a turn into traffic, and been looking at the sidewalk because the car has that much power. Sometimes I think I went a little too far on the power side of things....Nah!
