First off:
For All 1970-74 E Bodies there are only three (four) different types of K Members.
1) All 426 Hemis
2) All Slant six engines
3) All V8 engines
I said four because 1970-71 440+6 had a skid plate added to the bottom (some 440 4 bbl's too)
So if you have a 318 K frame, it's no different then a 383 K Frame and if you add a skid plate (available in reproduction) you would have a 440+6 K Frame.
I wouldn't pay more then $100 for a regular V8 K frame