Did you say; 30" tires and 3.21 gears?
That is a match made in hell.
This equates to 2.89s with 27s. Do yourself a favor and install a Mopar overdrive trans with 4.30 gears which will equate to 3.87s with 27s, and that will punch a big fat hole in your no-performance wall. And in overdrive, it will still cruise at 65=1950. So you can use one of those stump-puller cams.
If you install new low-compression pistons in those open-chamber heads, yur looking for a very disappointing bottom end, which will require a higher stall convertor, which, I hear, are hard to come by for the lock-up transmissions. So don't give away your cylinder pressure.
What that 318 needs, is Cylinder-PRESSURE. Your first offense for pressure is to get rid of the open chambers. The Second is taller high-compression pistons, and third is a tight-LSA cam. These three together can make or break your 318 combo.
The open chamber heads can be made to work with specialty reverse-dome pistons with raised Q-pads. If yur doing pistons anyway, this is one way to keep your open-chamber smog heads. and honestly, for this combo, you do not need more head than you have.
My advice is to no-way install any wide LSA camshaft, it will only kill your bottom-end power, and make yur midrange lazy. This will be unbelievably exacerbated by the combination of 30" tires and 3.21 gears. Don't do it!
If it was my truck; I say;
If it was my truck;
1) no question she is getting an A500/518 and at least 4.30s
2) I am selecting a low-rpm cam, but of around a 106 or less Lsa
3) I'm choosing a Solid lifter cam which will give me four things; 1)more pressure than a similarly sized hydro, and, 2)the ability to fine tune the rpm of peak power (within a small range of course), and the ability to fine-tune the pressure.and 3)size for size, I may gain some lift out of the solid, and 4) she'll rpm better. and 5) If the power peaks at 4800, with my gears being 2.45/1.45/1.00/.69od, the rpm drop from First to Second is to a stinkin 59.18% so;
shifting at 5000rpm/38mph, the rpm drops to 2960, and if she don't got no cylinder-pressure, that's gonna be a stinking performance problem, even with the 4.30s.
This 318 will want to get into Second gear, someplace north of 3300.... which will require a shift rpm of about 5600 rpm (now 43mph). So the little 318 is gonna have to, occasionally I'm sure, go there. Top of Second gear in this combo is 65mph=5000rpm, about a perfect as it gets.
The 2-3 split is better. Holding Second to 5000 rpm, the Rpm drops to 69% so to 3450 this time. But I hardly care cuz at 65mph, my "race", is over.
3) I am cranking up the pressure, right up to the WOT detonation limit of 89 gas, and I will deal with detonation if it shows up. If it doesn't, I'm going to 87 gas.
4) Ima running long-tubes and dual 3" exhaust with the long Dynomax turbo 3-pass mufflers, and full length 3" tailpipes. Ok maybe 2.5zzzz
5) on this combo. I'm gonna try my Offenhauser DualPort with the big Thermoquad on top; and she is getting fresh cold air from NOT under the hood.
6) if I decide to run those factory open-chamber heads, then KB has the step-pistons I will chose and I will machine them to fit for a tight-Q. but
7) honestly, I'd rather get me some alloy heads, flat-tops, and run the cranking-pressure up closer to 190psi, these will also allow more intake duration, and more rpm, and thus have a fatter, flatter power peak.
8) I will be doing some oiling mods for long rod-life, valve cooling, and a 7-qt oilpan.
9) because the cruise rpm is so low, I will need a stand-alone ignition computer, to optimize the cruise timing for max fuel economy ..... or I might swap out the 4.30s for 4.56s .. Oh yeah. with hi-flo alloy heads I am definitely going 4.56s. Cruise will be up at about 2200rpm, which may be cruise tuneable without the computer. I may need an oil-cooler back there , so I guess I'll keep an eye on the temp.
10) because she is now capable of cruising, I'd probably install a second fuel-tank. and for me, I'd be inclined to ditch the 4wd stuff, but, maybe not, lol.
If it was my truck;