Hy REAL RAT FINK, firstly please remember to tell us what year, size, and marque, [Chev or GMC] that you're asking about. I checked your profile, and I assume your asking about a 350 into a 1958 1/2 ton. Most of the 350 engine blocks I have seen have been drilled and tapped to accept the 55B-59 Chev V8 front engine mount brackets. The mounts will not clear the largest of the balancers, but you can swap to a smaller diameter balancer. If the truck did not come from the factory with a V8, you'll have to install two brackets on the frame for the lower part of the mount, all the parts are available from numerous vendors, hope that helps.
