Heads Explained

Cylinder Heads, "LA"
Aluminum Assemblies, Requires Head Bolt Set P5153851.
1 P5153849 Cylinder Head, Aluminum, 63 cc Combustion Chamber,
2.020"/1.600" Valves With HP Springs, 1967-1992 "LA"
318/360 Engines
1 P5155639 Cylinder Head, Aluminum, Bare, Used in P5153849
1 P5153850 Cylinder Head, Super Commando, Aluminum, Machined and
Assembled with 2.080" / 1.600" Valves (5/16" Stem) with HP
Springs, Use Rocker Arm Set P5153995, "LA" Engines
1 P5155128 Cylinder Head, Aluminum, Super Commando, Bare, Used in
P5153850

i'd save up your money and get a set of aluminum heads and intake when you are able. just go with what you have until you can afford the good stuff.
a set of P5153849 will cost $1800 bucks. comes with springs, valves, retainers all ready to bolt on.
if you stash $50 bucks a week (skip fast food) in 36 weeks you will have some badass heads... or use your income tax return to help fund them

i would not spend extra dough on the iron heads, like $300 or more for valves and stuff

you really want 2.02 valves if you can get them, they make a difference