[Dick Boneske]

IIRC, 1969 or 1970 was the first year of the multi-bolt motor mounts. I remember back in the day trying to exchange the 455 in my '70 GTO for the 389 in my '64 GTO. The 455 block did accept the older motor mounts, but not the other way around. I couldn't get the motor mounts to work with the '64 block in the '70 chassis.

So, there I was in my driveway in about 1972 with two GTO's without engines on a Saturday, knowing I had to be at work Monday AM. I abandoned the whole project and put both engines "back where they belonged." Not one of my best memories.

[GRX]

Exactly. A friend's uncle offered me $300 for my 389. Too low, and besides it wouldn't fit into his '74 Bird, which had a SBC when he got it.

[Bluesugar]

This is all true for originality but there are mount adaptors made that will let you put any Pontiac engine from '59 on into any "A" or "F" chassis....I'm pretty sure '69 was the last year that Injuns came with just 2 holes either side of their block

[GRX]

Pretty sure you are about about '69 being the last year for 2 holes. Not certain, I believe the '69 blocks had the bosses for the extra mounts, but only some were drilled for such. The mount adapters are pretty simple really. Should be no problem fabbing some up.

[Baron Von Zeppelin]

The 389's had less meat on the main caps and main cap bolts. (than the 400)
Cant remember now if the 400 head bolts were beefier or not.

But 389 usually had plenty of meat in the bores.
And most all had those sweet arma-steel crankshafts.

Great (terrible) story Dick Boneske. yikes lol

In early 80's a local kid built up a 68 WT for a 71 Bird.
He told me about it halfway through - and told him it wouldn't bolt.
...and when he finished . . it wouldn't bolt.
Bought an adapter mount set deal from H-O , and then factory breather wouldn't fit under hood. Changed back to stock intake - said hood still wouldn't shut ?
Bought a triangular ultra low profile breather and finally he could drive it with a hood on it.