Originally posted by techinspector1
Contact these guys and ask them.....
http://www.blowerdriveservice.com/techcharts.php
This is a chart showing the boost you can run with a given c.r., but I don't know about propane. I think it is the equivalent of 104 octane fuel. If that's the case, you could probably run quite a lot of boost, but I would be concerned about the motor spitting the head gaskets out if you don't o-ring it.
lsm will not just spit out but i do not know how the head bolt pattern is no the 392 but i have run 16.8 with stock 1017 felpros. O rings are more trouble. if you can use the cometic i would. O rings are a pain