Originally Posted by Astro350SS
You cannot use the factory engine mounts, as the sbc is 3 inches longer than the 4.3 v6. You can use the factory frame mounts, and the transmission stays in its original location. The only cutting you have to do is to the fan shroud to clear the accessories.
Hey Bill, welcome to the site. Have you been to
yet? Tons of info on the Mvans there.
I have to disagree with your above statement that I have highlighted. You can
use the stock V6 mounts. It takes a little bit of fabrication but it is easy enough to do and it is basically free. I also like the idea of NOT cantilevering the V8 over the stock V6 towers. I take the stock V6 engine brackets and bolt them on the opposite side of the V8 block (left to right & right to left). I then unbolt the passenger side cradle tower and move it 3" forward. I just redrill the three holes 3" forward and bolt it back down. The drivers side tower can't be moved because there is no cradle to move it too so I weld a 4x5 piece of 1/4" plate flush to the top and move the motor mount forward. A gusset down to the crossmember from under the new plate makes it pretty stout.
The actual disconnect from V6 to V8 mounts is 4.5". Swapping the brackets side for side takes care of 1.5" and moving the tower and motor mount forward 3" takes care of the rest.
We have done this with a bunch of Small and Big Block conversions and have had zero durability problems...
I am in the process of building a Pro-Touring Astro right now. It is going to be a pretty radical piece with a fully fabbed front and rear suspension, Big Block set back 14" and down 5" and (possibly) a quick change rear.
Welcome to the club.