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Just wondering.
Is there anyway to match a SM420 tranny from a 66 C20 pickup to a bigblock chevy engine??
Will I just tear up the tranny or shell out my rear end?
Or is it just not going to work?

I've heard a 6cyl flywheel will fit on a 350....will it bolt onto a big block & still work? Then I wouldn't have to change bellhousings & clutch stuff.

I know a guy who has a 366ci Chevy big block for sale and thought that would be great to put in my 66 Chev C20 pickup. We have them in grain trucks & they have great torque.

Any help is appreciated.

The SM420 is a pretty tough transmission, but it was not designed for the kind of abuse a big block can hand out.

A friend of mine's dad ran a 396 in a early 60's 1-ton truck with an SM420 for years with no problems.

So my conclusion is that your success will depend a lot on how you drive it.

Yea I won't be grinding gears or drag racing,but I might pull a trailer sometimes.
Do you have any idea how to match everything up?

Anyone else had expiriece with this??
Thanks everyone.

The bigblock should bolt in fairly easily, with the exception of maybe an engine mount. Keeping the coolant temperatures down will be your main concern.
Unless you load it heavy, I don't think your truck will get enough traction to tear anything up but the rear tires. I've got a built 454 in my 4X4 and never had damage to the drivetrain, except a u-joint got dry on me and made some noise.
Scott

Hey 48bigtrucks,
What did you have to do to match the tranny up to the big block? Did you use the SM420?
What did you have for a radiator??
Thanks.

I can't tell you how Scott built his, but the stock bellhousing in your '66 will bolt to the big block. A 454 is externally balanced, meaning you have to use the 454 flywheel for it, but the other big blocks are internally balanced, so your original flywheel should work.

The stock V-8 mounts for a '66 should mount the big block just fine. If its a six, know that the 230/250 mount differently than a 292. The mounts may be the same, but only need to be moved, but I'm not sure about that.

Years ago I ran a mildly modified 350 in a '70 4x4 Blazer. I drove like a kid in those days (probably because I was one) and broke the transfer case twice and destroyed the front drive shaft once.

I abused that truck a lot, and it would break...