Before you do that just check which cylinder is back firing(is it the low pressure cylinder) you may also have a ignition timing issue as well as a low compression.
Well guys I got the beast running.Was way out of time for one thing,carb needed a little tlc,but it does run.Having a few issues. Right side exhaust seems to be hotter then left,going to check plugs and wires also reset timing then I guess recheck compression.Dont sound bad after setting for 8-10 years.