My opinion: Either will drive both tires (as long as the posi is functioning properly). I have a friend with a J/SA Pontiac with a posi. Video shows what we suspected, it needs to be rebuilt as the right rear doesn't seem to be engaging properly. We're going to replace it with an aluminum spool. On a low HP application (maybe I should say low torque), I believe every effort should be made to reduce every once of reciprocating weight in the trans, driveshaft, rear-end and wheels / tires. If it were my car, that's what I would do!
Good luck...
NHRA #7494 SS/H
1970 AMC AMX
"Best Appearing" @ NHRA '06 Pacific Sports Nationals
JeffLeeAzRealty@Qwest.net
602-418-9797