Installing 1956 300 crop row engine into 1940 H

I need a little incite from someone that has more knowledge than what I have. I have owned my 1940 Farmall H since 1975 s/n 39402 and it always burned oil #2 cylinder. When I bought it, it wasn't running, I had to replace a broken hub clamp, replace the mag caps points condenser, then plug wires and spark plugs. Had to rebuild the carb just to drive it home. It had a rod knock so I slipped a set of rod bearings in it. Through the years I rebuilt the head #8043 with new valves, guides, and springs. Install a small diameter alternator what was used on Chrysler products and also used there solid state regulator. Later in time as the magneto got weak, I bought a distributor 90 degree angle, which was junk, so I took a 360 ci Chrysler distributor "no vacuum advance" and machined it to work then filed every other lobe off the reluctor and used every other terminal on the cap. I used a Mr Gasket spring kit using the light springs which brings the timing advance close to the production curve. I used the Chrysler E.C.U. also. Enough history. I want to put a 1956 crop row 300 engine s/n 57639 into the H chassis and found some differences. Mainly I bought a 1940 H distributor/ Mag drive and found the bolt pattern was smaller than what was used on the 300 front cover. So one of my questions is, can I put a "H" front cover and cover plate on this 300 engine ? Crank seal the same or different ? Pulley the same or different? What other differences will I stumble into. Thanks Jerry

During the year 1950 the ignition drive was changed and ones newer than then used on H and SH tractors will work right on the 300 engine.
Drive housing you need will have 6 numbers ending in R1. Early housings have 4 numbers and a suffix letter or 2 letters.
H and 300 engines use the same fan belt but pulleys are a different size on the crank and coolant pump. If pump or crank pulley is changed the matching other part needs changed also or a regular belt will be the wrong length. H crank pulley won't be marked with timming marks for advance like the 300. IH limited 300 gas engines at 22 degrees maximum advance at the crank. Since the generator pulley drive on the 300 coolant pump is a little larger than the H you may need a different length belt. PCV hose run from 300 valve cover to air cleaner inlet. 300 governor control arm needs replaced with the H one. Adapt size of air inlet to carburetor. Rework choke rod to other side of the carburetor.
Need to make sure the 2 head studs that the H throttle linkage mounts to stick above the head enough on the 300 engine. Depending on the manifold the throttle linkage that passes behind it may need bent a little for clearance. May need to use the top coolant pipe that works best with the top radiator brace on the H. Put the H oil pressure line fitting in the 300 block.
Could have forgot something. Post back if there's a problem. Someone will know what to do.

The advantage of the 300 front cover and accessories is that you can use a live hydrulic pump and that is a big advantage. If adapting the distributor is your desire, the distributor itself (from your modified mechanism, would work in a 300 drive housing from a 300 that had no hydraulics, or a post 1950-1/2 H or stage 1 SH. That drive housing would not allow a hydraulic system because it is from a tractor W/O live hydro. Jim