Reg. crank or sg style crank

[jjmag26]

I'm looking to buy a new engine and need to know the difference between sg style crank and reg crank. I think I need a reg. crank but I would still like to know what a sg style crank is. Thanks for putting up with my beginner questions.

[-=ADA$=-]

regular is threaded all the way, and SG has about 6-10 threads (dont remember) and rest is without threads, with reg one you need clutch nut with the pilot shaft, and with SG one you need only clutch nut, tell what engine is it, and what car it will be easier