There's a guy around my parts that did a 4bt swap in a ranger. It was no small task. Actually he was the second owner of it as the first guy got sick of sinking money in it. Drive train wise, nothing is stock. Nv4500 and dodge t case, custom springs up front, custom Drive shafts, and the part that killed me was the 4 inch body lift to clear the engine. Took him a few years to get it sorted till it worked right and was reliable. I'm 90% sure he had said something about swapping a heavier rear from a v8 explorer in it as well. Cool in concept but there are better enginse suited for that size of vehicle. The cummins r2.8 comes to mind immediately, as well as a 4tnv yanmar. Actually a bigger kubota may work decently as well. It is a really cool little truck, but not worth the effort when you can drop it straight in a half ton and not have to go through all the crap he did to get it to work. I've considered it a few times for my expedition but the cost of a nice used 4bt holds me back. Almost as expensive as a 6bt and makes way less power and doesn't have nearly the after market support as the 6bt does. To put it bluntly better not be squeamish of the conversion parts cost. When I did my 12valve swap in my 79f350 half the cost was getting the driveline to mesh properly. $2k for a nv4500 to grenade it after 200 miles. Few driveshafts till I got a combo that worked. Heck a 241dhd t case set me back $1500. Then a cool $1800 for a twin dusk clutch to hold up to it. Gets expensive really quick.
So here's my perspective coming from a guy thats owned or driven most ford and dodge diesels, as well as small and big blocks. Dodge sucks save the cummins. And the trucks themselves suck. Ford never made a good small block for towing untill recently, the 5.4 and 6.8 were and are turds. The 6.4l was the worst diesel Ford ever released, and showed when they dropped it after a few years. Can't say I even want to tow with anything small block hence why I still have my 460. It doesn't pull like a diesel but I don't have issues dragging 15k up a hill either. I'd much rather have the diesel. All costs side by sade the big block has been cheaper on everything save gas. 7mpg when towing heavy and 10 when empty closes the gap pretty fast, coupled when I'm done with a vehicle it's ready for the scrap yard. My current 460 has 190k on the clock and I doubt it will get close to 300k like my cummins surpassed years ago still running just fine. Heck when I pulled it apart to go over and o ring the heads before I stuffed it in my 79 we ended up reusing just about every thing save bearings and ring. It had basically no wear. Mains were spot on, rods were perfect, bore was great, pistons were good, crank was good, no cam wear. The oil pump speed out good but was cheap insurance to toss a new unit in, Heck it still had the original water pump and oil cooler from 94. If I want in search of big power it would still be together running just how it did before it got tore down. I was very impressed with it, and it didn't have an easy life before I got it. I'd easily go back if I could afford another truck with a diesel in it, but they cost stupid money just to buy. For now the big block works fine till I can afford a newer diesel. I'd buy a 6.7l Ford in a heart beat if I had the money on hand. Don't even think I'd modify it, they run great from the factory.