Wrong choice of words. I wouldn't buy a kit, I'd piece my own kit together. Such as Scat crank, JE pistons, Manley rods, Total Seal rings and Clevite bearings.
adperformance.com for stroker kits. Eagle 4340 forged steel cranks and H-beam rods. Their cranks r neutral balanced and the rotating assembly is good to 1000hp.
u could also go Scat. Try to find a 351W Mexican block and I would do a 408.
A good kit has the same components as one you piece together yourself. Example, my kit came with Eagle 4340 crank, 4340 h-beam rods, and JE forged pistons. What more do you need? Scat and Eagle have the best kits out IMO.
Don't know if Eagle still makes this kit, but I purchased their 418 stroker kit #14127 many years ago and been beaing the holy hell out of it ever since.
Easily take a 200 hp shot of happy juice.
You can put together a kit with one of Eagles new 4340 internal balance forgings, Eagle 4340 H-beams and your choice of pistons, H-series bearings and a good file to fit plasma moly ring set.