No aftermarket block. I have both RB and B blocks.
Running a 498 with 720 dynoHP in the Fed, works like a charm!
Setting the valves and one oilchange every season.

Cuda, -70
Valiant-65 AWB,
Valiant Signet200 -65 Topchopped dragcar.
Topolino Fuel Altered.
NostalgiaFED Sold,
SuperComp Bantam Altered, Sold
Ex Harlan Thompsons Nitro funny car American Graffiti Sold,