I'm going to respond to the question about the A518.
Don't do it. Not unless you like rebuilding the overdrive unit frequently, that is. The OD unit in our '90 B250 with 360 and A518 exploded. The rest of the trans, basically an A727, was perfectly fine.
Of the 14 Dodge B250 and B350 vans in the junkyard, NOT ONE still had an overdrive unit. Every one was removed, including the three that were pulled and then thrown aside because they, too, were exploded.
If you can find a Gear Vendors overdrive unit for an A727, grab it with both hands, but don't even think about a Dodge OD unit.
