I’m doing some mixing and matching of parts that I think are undamaged / unaltered but would like to make sure. On the left side mount for a big block in a B-body, is the corner marked with blue tape supposed to touch the block?

There’s considerable slop in the bolt holes so it can be positioned away from the block but I assume with the weight of the engine on the mount it would tend to eventually nest against block regardless of the initial position.

Grind a little off it, I wouldn't want that vibrating against a cast iron block.

make sure you use correct size bolts, I believe they are 7/16 dia. most people use 3/8ths

I have the factory 7/16 bolts. After a further look I think its a case of how tolerances and fits were just looser back in the day. Based on measurements from the right side mount I believe the mounts are intended to sit at 45 degrees or in other words parallel to the cylinder bank.

When I position the left mount at 45 there’s about a 1/8 gap between the block and the mount. Not sure how I’m going to do it but I’m going to try to figure out a way to maintain that gap.

Usually the part that goes on K-frame determines where the engine part of mount rides. I snug the bolts on block then while keeping support on engine I tighten the frame mounts then engine. Just seems to align better that way.

I’ll probably go this route. It will save me a few hours of analysis paralysis. As a side note, while taking measurements, I discovered my NOS Polyloc mounts are about .100 shorter than factory mounts