I'm looking for a crankshaft to make a 383 for my truck. No Hi-Po stuff, just cast crank that will never see over 4000 rpm. I came across a crank that is advertised as externally balanced front and internally balanced rear. Uses 400 balancer and stock 350 flexplate. Are these cranks any good? I have never heard of such a beast and thought I'd get some opinions here. What's better this type or completely externally balanced crank or a completely internally balanced one? It's also going in a one peice rear main seal block. I also noticed my stock 350 flexplate has an odd shaped weight welded to it. Will this affect anything? I also have a 400 balancer and flexplate so that's not an issue. but I'd like to stay with the stock 350 balancer and flexplate.

Bunjy,
Are you sure that the crank you are speaking of is available for a 1pc seal block ? Usually, those cranks are the old style and have a HUGE flange counterweight to allow the use of an old style 350 flexplate. Your one pc seal 350 is externally balanced on the back ... thats why your flexplate has the weight on it. If you wan to be real technical about it, even the old 2pc 350's were externally balanced in the rear ... thats why they had the "oblong" shaped crank flange.
Your best bet, both price wise and compatibility is to buy a complete balanced rotating assembly from someone like Eagle. That way you will know that everything will fit. They have 383 assemblies for the one pc seal blocks.

I now can't find the original I saw on evil-bay but here's one like it. This one doesn't specifically state internally balanced rear but does state use 350 flexplate. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33616&item=7928171440&rd=1

What he isn't telling you is that crank will balance with a 350 damper & 1pc of tungsten in the front & the standard late 350 weighted flywheel at about an 1830-1850 bobweight which is pretty light.
You are probably going to have to add Tungsten to most parts combos unless you use pretty light pistons which is fairly expensive.
It is not a drop in crank.
Also I am a bit leery of the price as I am a dealer for Scat & know what they cost.