U MM conversion to 336

I have a U MM that I'm turning in to a pulling tractor. I bought a M670 engine to use for some parts. I'm needing some help and advice.
Which rods should I use? The original ones or the those from the the 336? Can I use the push rods and rocker arms from the 283?
Where should I go to get overbore 336 pistons? Does anyone have a recommendation on having the camshaft ground? Do I need to get a gasket kit for both the 283 & 336 engines. I plan on using the original crank, crank case, the 336 blocks, the 4232 heads and manifolds from M670. Which carburetor should I be looking for? Are there any other issues to consider when making this conversion?

Thanks for any help on this.

Using 283 crankcase: 283 rods (336 is
different size journal) ,336 head and
jug gaskets, either carb., either
rocker assembly, most likely the 336
pushrods to get proper length. I am
not a fan of reground cams.

Sorry: forgot to mention you may need
thick or double jug gasket to prevent
piston from traveling above top of
jug. This is a fairly simple
upgrade. Take your time and think
things out. Molines are a "big boy
erector set."

Do you have/ want to sell the 283 jugs and possibly
pistons? My ub needs some parts.

Sir,
You use your U rods in the conversion. If the pin bushings are worn, just press in some #10A9105 bushings and hone them to size.

Oversize pistons for those 4.625" jugs are available in sixty, ninety, and one eighth inch oversize. Your original block bore was 4.626 inches. The FINISHED rebore sizes are as follows;
#60P46862843 piston has a 4.686 inch finished bore diameter.
#60P47162843 piston has a 4.716 inch finished bore diameter.
#60P47512843 piston has a 4.751 inch finished bore diameter.
All of these new pistons have the same 2.843" compression height as the original #10B4210, M5, G series, M670, etcetera pistons. If you plan on using the pistons you have; remember to count and measure the ring widths before asking for new rings. I know of several different pistons that were used by MM. Zolner, Federal-Mogul, Gould, and other piston suppliers; all used different ring widths and combinations. All are still available.

You just need to get some #10A16979-T crankcase to cylinder block gaskets. They raise the jugs one eighth of an inch after torquing them. This makes everything just proper, and no one sees those ugly shim plates. A regular #10R58 top end gasket, for a 403 engine, fills out the rest of the gaskets needed.

Use a #10A9465 intake/exhaust manifold to feed that new setup. There are several carbs that will work. You can also just drop in a new venturi and high speed seat in your current TSX67 carb. That makes it into a TSX68 carb for a 403 engine. There are dozens of choices, depending on what RPM you will be running.

Skip the cam stuff, unless you want to kill the lower RPM torque to get a little more top end zip. Drop in a set of new #10A9034S valve springs, for a cheap upgrade, that will give instant gains at all RPMs. Shimming springs is a ticket to disaster.

Happy Wrenching.
Charlie

Hi Charlie thanks for all the great info! As I dig into it I'm sure I'll have more questions.

Sorry I'm going to hang onto my parts for now. Seems like there's always more that. Need fixed.