I am replacing my 350 with a 455 for my 70 cutlass vert project I know you just have to match the SBO frame pads and put the SBO mounts on the 455.
Is there any advantage to changing the frame pads to the BBO frame pads vs staying with SBO frame pads?

 

Wish I had a dollar every time this is asked here. Do a search and you will get good info.

 

No benifits however just match what you have.

 

Thank you that's what I was looking for

 

2261 engine mount

 

Just to provide full information, the 2328 mounts and matching frame pads DO tuck the mount a little lower and further inboard, under the pan rail. This MIGHT provide a skosch more clearance for headers. Note how much of the 2261 mount sits above the plane of the bolts to the block (red dotted line). The 2261 is completely outboard of the pan rail. The 2328 is tucked under the pan rail.

 

I'll give Joe his thoughts on that however my 66 has small block pads and mounts and header clearance is almost a non issue other than steering rod.

 

I wasn't suggesting it was necessary to use the 2328s, just that if one had a situation with large diameter headers, its an option that frees up a little more space. Obviously every 1966 came from the factory with the so-called "small block" mounts (2261s).