Plate between motor mount and block on K10

[benoit454]

I have an 86 305 k10 with a 700r4 and just recently pulled the 305 to put in a 350 once rebuilt.

I noticed the 305 mounts had a 1/4in. or so plate between the clamshell moutn and block.

What is this for? They have one on each side, and a bolt hole in back, the are both slightly different though.

Do they need to go back in?

I had a 76 2wd and it didn't have them.

What would happen if you left them out?

I can get pictures tomorrow if anyone needs them.