What will it run

The 4900 stall speed I was seeing with my 8” converter behind the 340 wasn’t really enough.

Behind a 383 with a 256/262 cam, in the same car but with 4.56’s that 8” converter would flash about 5400.

That combo worked pretty well, with 60’ times in the mid/low-1.50’s(1.51 best).

“if it were me”, I’d replace the 272/280 cam with something quite a bit shorter, then revisit that converter afterwards.