distributor

Confusing, yes; but he did name it correctly. DUI's slant six distributor is called a "Tri Power" by the manufacturer and is just a model name, maybe a reference to its three-wire hookup or something, but not a reference to carburetion.
Dodge Slant 6 Tri-Power Distributor – Performance Distributors
It does sound like a timing issue, I'm just not sure what's meant by "10 over TDC"; it's normally referred to as before or after TDC and that could be an issue.
Is it backfiring out the exhaust or popping back through the carburetor? Or if it is a misfire, as you say, are all the plug wires correctly located in the distributor cap and fully seated?
Was the timing set with the vacuum advance disconnected and the line plugged?