Yes and yes....
The 4.3 and the 5.7 are both internally balanced and use the same flywheel.
The 4.3 is basically a 5.7 with 2 cylinders missing.

Signature
Mad-Dog
'79 Chevy K-10
Slightly modified
pictures can be found here:
http://mad-dog16.tripod.com/
--
> Does the 4.3 use the same flywheel as the 350? Also is it the standard
> 168 tooth or is it different?