512 stroker.

At the risk of repeating whats already been said,
if you buy a kit from 440 source, have it CHECKED thoroughly by a performance Engine Machine Shop, moreso now imo, than even a year ago.

I've probably seen 10 kits or so brought into my shop by Customers in the last couple of years,
the 2 Kits I've seen so far this year, were both UTTER FAILURES, in terms of Machining Quality and Balancing.
Absolute GARBAGE that required not only regrinding the Crank, Re-Sizing the Rods, and Pin-fitting, but a complete Re-Balance as well ?
The only things OK were the ICON Pistons supplied in the Kits.(Pin-Fit good to go)

IMO,
440 source Kit quality has dropped DRAMATICALLY of late, be careful.

Some "cost-effective" Rotating assemblies they were ?
Thats 2 in a row so far this year.
J U N K !