Looking for predictions and estimates...

Looking at your combo:
"1972 340 Duster
3000 lbs with me in it
727 trans with shift kit
3500 stall 10in tc
bored .30
stock crank and rods
300 duration solid lift cam stock rockers (3500-6000rpm)
11 to 1 compression forged pistons
HP 340 iron exhaust manifolds 2.5in pipes with carter mufflers
iron heads ported with 1.96int 1.60 exh
aluminum M1 single plane port matched
700 double pumper manual secondary
holley hv fuel pump
4.30 rear ratio 8 3/4"

The items above have 12.50 - 11.50 potential...

"aluminum rear wheels mickey thompson L60 14 indyprofile (295/60 14)"

This item has 13.0 written all over it...

Get some slicks or DOT drag radials to reach the potential of the rest of the combination.