Only the early 4.3 even fire engine had no balance shaft. I want to say 1993 and up had them. But you can use the vortech head on the early block and they flow so much better.
The we have the odd fire. That has 4 bolt mains and way more cam. They were nascar engines for the Bush series. Once that went away so did a lot of parts.
See my build thread for parts and changes. http://www.mightyram50.net/vbulletin...Chevy.-4.3L-V6