Strokers should all be internally ballanced. You should use a ballanced flywheel, of course, too. 434 I think is tough to get, an easier stroke is the 427 which is a great motor. You're only talking 8 cubes anyway. I think there's one of two issues to overcome. The block will definately have to be notched to accomodate the stroker assembly, but the exact details of that could probably be handled by your machine shop. Secondly, special rods, a small base cam or both must be used. Remeber if you use a small base cam you'll have to re-measure everything in the valvetrain and get different pushrods.