86" Sierra K2500 motor mounts not lining up

[fang508]

So I have this 86 sierra k2500 that used to be a diesel. When I bought it there was a tired 350 in it with a lot of small but costly issues so I decided to put a sbc 350 crate motor in it. Before putting the engine in I ordered these mounts through Classic Industries that turned out to be the wrong set http://www.classicindustries.com/pro...ts/t83099.html . Instead I should have bought these http://www.classicindustries.com/pro...ts/t83132.html . The difference between these that the mounting holes do not line up 100% on the first set of new mounts while the 2nd set does. From what I understand that the 2nd set of mounts were designed for diesel/454 k2500s. The sbc clamshells that bolt to the engine meshing with the crossmember mounts has a 1/2" diameter hole. However, the center bolt on my diesel mounts is 7/16" diameter. The P/O had 7/16" bolts going through the 7/16" diesel mounts but since he had the a sbc the clamshells holes were 1/2" which explains why the engine vibrated and bounced around 1/4"~1/2" when idling. So my question is.. would it be a good idea to drill the 7/16 center hole on my mounts to ame them 1/2? I would only be taking off 1/32" of material off on all sides and there would still be a rubber liner in the mount. Perhaps if I didn't have an original diesel truck this probably wouldn't be an issue. Thanks, and sorry for the wall of text.