you need to elaborate a bit about this 'cross member', and where the rivets are on the 283 - the 283 and 350 blocks are enough the same, you should be able to put the 350 right in where the 283 was, nothing is riveted to either engine
the only cross member that might be required would be for the trans, and there will no doubt be a difference between a 4x4 and a 2wheeler, but that doesn't affect bolting the 350 to the original 4x4 trans
is the 283 mounted at the front? if so you can unbolt those mounts from the 283, and bolt them onto the front of the 350, should only be the brackets on the frame that are riveted .... if it's mounted at the sides, the mounts will still bolt to the block, and the mounts themselves will be bolted to a mounting bracket .... GM didn't rivet engines in
got pictures?
Bill
