How much weight is the front of a 46 1 1/2 ton rated for? I was going to make it into a gooseneck puller but the flathead is too wimpy, wimpy for the retarded loads I pull on my trailer (usually around 25,000#). The truck would be an improvement over what I do it with now, an 88 3/4ton disel, ford of course. I considered putting a 7.3 in it but that obviously wouldn't be an improvement in power which would be nice. I would love to put a big block Cummins or 3208 Cat in it but I'm affraid of the load on the small front axle. They did put huge V-plows and stuff on the front of these trucks though didn't they? I have never even rode in a truck this old so if you think I'm nuts for thinking about pulling a trailer with it let me know. It would be to turn heads and get attention for my repair business more than anything, I'ld buy a powerstroke if I just wanted to move stuff but what fun would that be!:

 

I took apart a 46 2 or 21/2 ton Ford for parts on my pickup. The front frame rails were beefier on the big truck, but just as narrow as on my pickup. Also, the cab location relative to the engine looked to be the same.
I installed a 292 yblock, with considerable difficulty. Using a manual transmission, and with the steering box location, there was no clearance for the left exhaust. It had to go through the inner fender. Clearance between the right aluminum valve cover and cab was zero. Had to grind down the back of the valve cover. Fan location behind radiator too low. Need electric fan. Distributor interfered with firwall. Modified distributor and firewall.
Replaced stock steering box with Vega steering box to gain exhaust clearance. Clearance still very inadequate and now need to worry about decreasing engine weight to compensate for steering box design. Oil filter interfers with steering box. Had to install a very undersized oil filter until a remote unit can the purchased and installed.
These are just a few of my experiences. It seems to me that the difficulties you are facing are considerable. Best of luck.

Mike