The GM I.B.S. with just a little work will fit the Lyman GP rifles.
It's a simple matter to remove the single underlug and reposition one or both underlugs for the Lyman,you must also cut back the under rail and it is best to redrill and tap for another small screw to hold the rail.
Track of the Wolf can do it for you. Best guess 100$ worth of smithin or $40 worth of tools,time and patience.
Why do you need a fast twist?
A round ball work just fine with game up too deer size out too 100yrds.??