[silicon212]

Rocker arms - you do not want aluminum rockers on a street car. Period. They do what they do well, but don't have the longevity for the street. Factor in about 3-6K miles on a GOOD set, so stick with the chromemoly roller tips. In this regard, the Magnum rockers from Competition Cams / COMP are very good and are recommended. They are what I use on my car - and the set currently installed has over 250k miles on them - that's a quarter million - still going strong.

Heads - the only heads you can safely mill are the pre 1978 ones (if your heads are stock, you're golden). These can be differentiated from the earlier ones by looking at the area under the spark plug - the good (pre-78) heads have the edges generally even across while the later heads have "notches" between the 2-3, 4-5, 6-7 bolts along the bottom. Also, on the underside (the deck surface), the water jackets on the good heads are drilled in, while the later heads have cast-in ports along the intake side of the chambers (the quench area) that are trapezoidal in shape. The later heads are called "lightweight" heads because the deck surface is thin and cannot be milled very much - these heads are also quite prone to cracking. I cannot remember what the casting number is for a set of these older 305 heads as it has been about 18 years since I've worked a pair, but something tells me "334" are the relevant numbers to look for.

Roller lifter cams do not require initial break-in in the way that flat tappet lifter cams do - so a roller cammed engine can be started and run at idle during initial start up. As for maximum lift - if you're going with stock rockers the max lift is in the .450 range at the lobe. Any more than that will require rockers with longer slots in them - if you go with the COMP roller tip lifters, you can use a larger lift cam. The biggest thing to look out for on any engine as far as lift is concerned is piston to valve interference. This is best checked with an amount of modelling clay added to the piston crown, the heads installed along with the intended gaskets, spinning the engine BY HAND for two revolutions, breaking down the heads and measuring the thickness of the clay. It's a little time consuming, but this will give you an idea of what you can run. Any cam with large lift is going to require stiff valvesprings - what is required depends on the cam maker - you want stiff springs to prevent piston/valve interference due to valve float at high RPM.

One more thing about roller cams vs. flat tappet cams is that you will need aftermarket rollers in an engine without such a provision (most blocks 1984 and older) or factory rollers along with the retaining bracket (1985 and newer blocks *generally* have the provisions for this, even if the engine is factory equipped with flat tappets). On factory rollers, there is a retainer that bolts to the front of the block (behind the timing sprocket) that retains the cam preventing "cam walk" which can occur with roller lifters. If your block doesn't have this, you will need a special "button" and timing sprocket. The button attaches to the inside of the timing cover, on the cam centerline, to prevent the cam from "walking" forward. Also, aftermarket roller cams, typically billet steel, require a soft, bronze distributor gear in place of the factory gear.