First off, I'd like thank you to thank you guys for your help and sharing your knowledge! When it comes to the super technical stuff, I am "dumb" but learning so I appreciate the patience!

Ok, so, if I am looking at things right, the gm springs though not adequate for high lift cams do have more seat pressure than stock mag springs? If so, would that add to rpm limit, durability, and HP?

Basically, I am building a junkyard dog. Unfortunately a crazy ex wife, a daughter I love to spoil, and a new wife and stepdaughter I love to spoil (oops I did again, lol) has left me....well...dang near broke! So my goal is more power and realability for cheap cheap cheap! If the gm springs are a little better I will get them from my pullapart here for next to nothing. The magnum heads themselves are only going to cost me 75 bucks from the JY! I am hoping that if I use the mag heads, upgrade the springs a tad, and use my factory roller, I will still see a noticable improvement in performance.

I did find some specs on the factory roller cam in my engine:
Part # 4323239 used in 2bbl 318's from 1985-1986
Lift (I/E) .391/.391. Duration (I/E) .240/.240

So if I understand correctly, the 1.6 rockers on the mag heads will actually give me MORE actual lift right? How do I calculate to see what my lift would be? How does spring rates and seat pressures affect performance? Why don't manufactures use better springs in the first place?

Sorry for all the questions, but when educated peeps like you guys are willin' to teach a dummy like me, well...