I have a 59 Dodge D100, 318 poly with a 4 spd. I am a builder and occasionally use the truck for work (and advertising). From what I gather, this is a somewhat unusual combo--1/2 ton with 4 spd. First gear is the useless granny gear. I also suspect it has quite a tall rear end. Tab is missing from axle so I can't tell for sure. I want it to be a driver, but the current drive train makes that difficult. Parts are very expensive and hard to find (just spent 225.00 on a fuel pump). The present gearing leaves it working very hard at 40 mph (I think there was a 4.10 available at the time, and I wonder if that is what it has). After being garaged for the winter, its first drive revealed a slipping clutch (replacements are 400.00). It also has a loud bearing noise coming from the transmission (not throw out bearing as it happens no matter the position of the clutch). Any suggestions for changes/swaps that would make this a more drivable, less costly and difficult vehicle? I love the damn thing and want to find a way to make it a bit more practical to own/drive.
5 on 4.5 BP pattern wheels by chance? Check widths from Ford Explorer 8.8 rear ends. Search for “the Ranger station” and they have a WMS to WMS distances listed for Explorers and Ranger 8.8 rears. Most likely would have to relocate the spring pads, possibly use yours for proper size. A little grinding and fitment would be happening. Welding involved as well.
You are being raped on parts costs. The A engine uses the same fuel pump as later LA engines. Carter M6866 is one of many available. Some variations in inlet/outlet locations. Where are you located? US or ? If you are asking about engine/trans swap then plenty of Mopar will nearly bolt in. Axle chart: Rear Axle – Quality Engineered Components
Easy to determine the rear ratio. Just jack up the rear on one side of the axle. Chock block front wheels. Put a jack stand or two under the frame. Put trans in neutral, release park brake. Now find some chalk crayon or heavy duty marker, ??? piece of masking tape? Slide under the back, near the driveshaft. Mark the shaft at the bottom near the diff. Mark the side bottom of the raised tire. Now push the tire around, one time, as it moves count the number of turns the driveshaft makes. The number of revolutions will likely be plus or minus a whole number. Try your best to guestimate the extra fractions ( simply said a quarter is .25, a half is 50 and 3 quarters is.75 ) Then you'll know that if it turns four or five times, changing out the carrier for a three something rear will get you down the road better.
There is room under the hood for pretty much any motor you like. Big blocks are nice but a 360 is a good compromise between power and gas mileage. Some years back I did a similar swap of a 360 and automatic out of a 76 pickup truck. I kept the original low geared rear axle, it worked great for around town and pulling a load, not so nice on the hiway. It's all according to how much you want to spend and what you can find.
No kidding on your mention of parts and cost. OP is paying an insane amount. At his $$ mentioned, I’d expect it as an installed price.
Your 59 should have a 8 3/4 rear. A lot of higher gear pumpkins available for that. although not easy to change with the nut and keyway axles. Find a 8 3/4 out of a 65 and up 1/2 ton pickup. A lot of the 70-71's had 3.23 gears, that would be much more highway friendly.
Without knowing exactly what you have for an engine in the truck and where you are at it is hard to make legitimate suggestions. If you are not in the USA, Canada or Mexico the options may not be what we would see as simple and easy to accomplish in North America. Snooping a bit it looks like the rear axle WMS to WMS (wheel mount surface to wheel mount surface) is 62-1/4 inches. That came from here https://www.qualityengineeredcomponents.com/rear-axle/ Pretty much the same width as a second gen Camaro That I did a swap for a guy with when I put engine, trans and rear axle out of one in a 56 D100 years ago. 65/71 D-100 are 63-15/16 wms to wms and that would probably be an issue with your rear wheels and tires that you have. A couple of Ford rear axle come close at 61 and 63 inch width. The Idea behind swapping to a rear end with a more road speed friendly gear ratio being the simplicity if you get the correct lug bolt pattern. You can play with this speed, tire size trans ratio, rear end ratio get RPM calculator to figure out what gear ratio in the rear end gets you the rpm at the highway speed you feel comfortable with. https://purperformance.com/p-29669-rpm-calculator.html This one lets you put in three factors and get the fourth but doesn't have a separate box for over drive and you have to figure that in if you are thinking overdrive. https://www.advanced-ev.com/Calculators/TireSize/index.html
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