The Mopar stock converters were high in comparison to other makes. The stock converters were typically around 1700 RPM while the factory high stalls were around 1000 RPM higher. They worked well, too.
I would look around for some 452s in good shape. They flow the same as the 906, but have the hardened seats for unleaded fuel.
I was wondering for the OE poster. If he has not a hi stall converter, the getting one, even a cheap one, well, kind of throws "Cheap" out the window some. ($$$ Dependent of course on the verter price)
Trying to work within the confines of Cheap and what he has allready, the stall of the converter limits the cam choices. For a cam choice, if the converter is a low stall, I'm guessing a OE road runner cam would be too much. Do-able, but a bit much for the OE low stall.
Also, Is there a hi stall for '78 model years? Not to thread hi-jack, but I have a '78 P code 400 & 727.
What was the gear ratio of this car again?
But if your block came with 516's, adding these heads will really drop your compression. Since the 516 had smaller chambers
Also hardened seats are not a requirement, unless you tow or have a motorhome. Larger duration cams in a car, also with correct tuning run the exhuast valves cooler. Along with less driving we do with these cars, you'll never need them.
Stock 2 barrel 383 had 8 to 8.5 comp at best.
I think Moper has a good idea. I would look at a wider centerline cam due to the low compresion. Huges says there whiplash cams will keep compresion up on low ratio mills.
Add intake of choice and headers. Run as is like Moper said until budget allows for a rebuild.