HELP! small block to big block swap

[Mr. GMC]

I have an 86 shortbed C10 I am about to put a 489 cu in big block in; the truck had a 350 in it; what mounts have to be changed? block mounts?, frame mounts?, frame mount towers? Any or all? This is my first big block swap so any other tips related are much appreciated. Also, this is going to be a 700 horse motor, so should I use solid mounts, poly mounts? I have heard that high horsepower big block chevys have been known to spin the main bearing where the motor mount is because of block/main web deflection. What about a front plate? Thanks again for any tips or advice.

[benoit454]

As far as I know the sbc motor mounts on both the frame and block are the same so neither needs changed.

As for solid or poly, solid would be the strongest, but alot of vibration into the entire truck.

I would think the rubber mount would break before you spin a bearing, but if you had solid mounts, maybe then it would spin, or with poly, not sure. I don't have much experience with either. A good friend of mine runs alot of big block, but in his malibu race car, he's always ran solid mounts in it.

[74 shortbed 406]

the only thing that is needed to be changed is the exhaust, if your sbc had headers your exhaust might bolt to bbc headers. With that much power I am gonna go out on a limb and say not going to be a dd. On that note if you go solid mounts or plate your truck will vibrate a lot. You may loook at some custom mounts. I know some of the mud racers are running custom mounts because of the stresses put through the driveline...