I've built many 383s...including the hyd roller project I'm presently involved in. We never build any 350s anymore considering 383s cost the same to build.
I've ALWAYS used a NEW 383 rotating assembly...including a 3.75" stroker crank that has 350 main sized bearing journals.
Wouldn't even consider using an old cast 400 crank!! With it you'll need to run main bearing spacers.
For a moderate performance build...the Scat 9000 series cast cranks are perfect. We've drag raced these for years without any issues.
Too bad you're not closer...I've got an extra 1pc seal block that has provisions for both a factory roller setup AND a mechanical fuel pump boss (rare)...all machining is done, bored, finish honed, align honed, stroker clearanced, new ARP main bolts, cleaned, Dura-bond cam bearings and brass freeze plugs installed and it's ready to assemble.