Welcome Randy.
Pretty sweet 65 you got there.
I'll tell you that beyond the numbers, a sure fire way to tell if you have a 273 Commando engine is to pull a spark plug and look in the cylinder with a Bore Scope and look at the Valve relief cuts in the piston top. If you have 4 valve reliefs, you will have a standard two barrel, low compression 273. If you have only two valve reliefs, it would indicate the Commando 273 high compression engine.
I found a harbor freight unit worked fine.