The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - So my all original 72 has a replacement engine block. What to do?

PGG · 03-12-2018, 05:59 PM

So I bought my 72 K5 Blazer 4x4 as an all original truck other then repaint in its original color before I got it.
Turns out the engine block is a 77-78.

So do I rebuild it with?

A. Build with this 77-78 4 bolt main block since I have it? Its standard bore.
B. Put in a new LT1 replacement and TH700 tranny?
C. Find a 72 4 bolt main casting and keep it as close as I can?
D. Buy a new warranted replacement?
E. Just F it and put a big block in it with 500HP?

I am leaning towards option C but no idea how hard that block would be to find and I feel like there is little upside to doing that value wise as I wont lie if/when I sell it anyway.

Thanks PG

PS, yes I am butt hurt if that matters I thought it was the original engine and there is no real going back.

03-12-2018, 05:59 PM	#1
PGG Registered User Join Date: Mar 2015 Location: Fort Worth Texas Posts: 279	So my all original 72 has a replacement engine block. What to do? So I bought my 72 K5 Blazer 4x4 as an all original truck other then repaint in its original color before I got it. Turns out the engine block is a 77-78. So do I rebuild it with? A. Build with this 77-78 4 bolt main block since I have it? Its standard bore. B. Put in a new LT1 replacement and TH700 tranny? C. Find a 72 4 bolt main casting and keep it as close as I can? D. Buy a new warranted replacement? E. Just F it and put a big block in it with 500HP? I am leaning towards option C but no idea how hard that block would be to find and I feel like there is little upside to doing that value wise as I wont lie if/when I sell it anyway. Thanks PG PS, yes I am butt hurt if that matters I thought it was the original engine and there is no real going back. Last edited by PGG; 03-13-2018 at 03:48 AM.