I run TF 8x6 , 9x6 , or 9x4 ( best ) on mine. In twins .
If its light & you want the 5.0 per lap bit , the topflite nylon 9 x 4 orIve used Zinger 9x5 woods .
This test ( sceptre flight ) is the later retimed one - Black steel prop driver .They wake up on 15 or 20 % nitro . & can run ' the break ' .
Think I run the heads around 7 thou. clearance . They varied a bit .
Yours is a earlyish , 1972 maybe , as only vertical weeny muffler screw thingos .74 ish on there fore n aft also . later undrilled on the up & down .