I will be buying new mounts for the fresh 455 going into my '70 Cutlass. I know both the 350 and 455 mounts will work, but does one type of mount set the engine a bit lower than the other? I'll be running an Edelbrock Performer intake, probably a Quick Fuel carb and an aftermarket OAI hood. (Sorry, Joe...) I don't know if I'll ever get the actual OAI intake hardware for the car, so I'm thinking more about air filter to hood clearance.

If one sits lower than the other, does that also impact how the headers will fit?

 

NOOOOOOOOOO!

Sorry, knee-jerk reaction.

Match the motor mounts to the frame pads, period. The block is irrelevant.

 

Hilariously, on my '72, the engine DID end up lower using the 2328 setup compared to the 2261 setup. I haven't spent enough time messing with them yet to understand why. I have normally had to buy multiple rubber mounts to find ones that actually fit correctly.

If you're getting new pads, then check the pad to mount fitment out of the car. I got DEA, Anchor and Pioneer mounts, and only the Anchor ones actually lined up with the frame pad. The others had too much rubber molding on the hook, and even after cutting that off I had to hog out the cross bolt holes.
These were also repop big block frame pads, so who knows which one is "more" correct.