1979 d300 dually specs

anyone know specs on towing or load capacity gearing and anything interesting on these trucks.We bought it to pull our car trailer.It has a b rake controller with a brake line to it.Are these good or bad?The guy said it was a rebuilt 318 but it has a factory 4 barell intake on it.I am wondering if its a 360.It seems to have a lot of power.

Open the door. there is axle ratings in the jam. Ratio is on a tag on the diff cover held on with one of the bolts IF its still present. It could have 4.10-4.88. Is it an auto or stick? Look at the block above the starter, the engine sir is cast in the block. Should pull almost and car trailer just fine. I used a regular 3/4Ton to pull my open car trailer with 318/4spd 4.10 grs. That style brake controller is the older style setups.

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It has a b rake controller with a brake line to it.Are these good or bad?

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Those are awesome. Here's the modern equivalent.

http://www.thoroughbreddiesel.com/dr-performance/brakesmart.htm

Robert