Yep- - - -trash the electronics and make it a "dumb" engine. The I6 flywheel and clutch should bolt right on, I believe. I don't remember if the 4.3 is an internally balanced engine or not, but I believe it is. Check the harmonic balancer and the transmission flex plate to see if there's any kind of offset balance weights.

OK- - - -just did a little research- - - -the same flywheel that fits a 250 I6 also bolts onto a 4.3- - - -and a bunch of small block V8's- - -305, 350, etc. Just swap the standard shift parts onto the 4.3 and bolt it in.
https://www.ebay.com/itm/265226751995?

Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!