The 55-56-57 the engines mounted the same way, 2 mounts on front and 2 mounts on the bell housing. I replaced my 283 mill with a 79 GMC 350 truck small block. I retained the original steel bellhousing, bell mounted starter, original flywheel, original ram horn exhaust manifolds and front engine mounts. I would think if you are using the same driveline components (stick shift or original powerglide trans) you should have an easy change over. The only thing that could be present a problem are the front engine mount holes if they are not drilled and taped which can easily be done. Good luck on your venture and happy motoring.

You will want to make sure that the 350 has the holes in the front of the block for the mount brackets. I believe you will be able to use the same engine mounts in the original location. The only thing may be that the 350 will have a larger diameter harmonic balancer, like 8", which would interfere with the original mount brackets that bolt to the engine. If this is the instance, you can notch out the original brackets to clear the balancer. Also, a 350 engine doesn't have any provisions behind the intake. So, you'll have to come up with a way for it to breathe.