Drilling C30 dually hubs for 5 x 8" wheels

[LynnB]

Sorry for the long post.

I have this really cool 1949 Studebaker 1.5 ton farm truck. I use it regularly. I have posted a few times over the last 7 years in the “heavy haulers” section, mainly because I replaced (engine swap) the old flat head six (96 hp when new) with the engine and trans out of a 1972 C50.

Could not be more pleased with the swap.

The rear axle is a 6.66 gear. My five speed is NOT the OD model. That means, even with tall 235 80 17 tires I am spinning at 5200 RPM just to go 70 miles per hour. Low gear is virtually useless. I normally start out in 3rd without a load, and even with a load, unless I am going uphill.

I have a chance to purchase a 4:10 rear axle assy out of an 80s C30 dually.

If my calculations are correct, a 4:10 rear with the same tires would get me right at 3200 RPM at 70 mph. Quite the improvement. Getting ready to call the seller and get all the measurements to make certain I can make it work. I am adept at fabrication, so no worries there. Just need to make certain the flange to flange measurement is in the ball park. Doesn’t have to be exact, as it is a flat bed (actually a dump bed, and it still works, which is GREAT when I haul a load to the dump. Don’t even have to get out of the truck.

I REALLY want to keep my wheels. I know the easiest thing to do would be purchase four 17 inch dually wheels in the right size, which I BELIEVE is 8x6.5" Bolt Circle with 4.56" Center Bore. But then I have to carry TWO spares, one for the front and one for the rear. Also, finding that lug pattern in a 17 is a challenge. Most are 16s, and I can’t do that as I have six almost brand new Michelins (take offs from a 3500HD) on the vehicle right now.

Chevy bolt pattern: 8x6.5" Bolt Circle with 4.56" Center Bore

Studebaker bolt pattern: 5 X 8" Bolt Circle with 6.050 inch Center Bore


What I am wanting to know is if the hubs on the Chevy rear can be drilled for 5 x 8" bolt circle.
I am not worried about the difference in bore size, as I can have hub centric rings fabricated to make certain the wheels are centered.

Anyone have hubs bored for a larger bolt circle?

Is there even enough extra metal to go 8 inch?

Thanks in advance for any help.