Gotcha. If the oiling in the engine was that bad, then I wouldn't give another thought to the old pump or the gear on it. I've put something like 60,000 miles on a Melling M66C driven by an aftermarket camshaft (from a good manufacturer), including hundreds of hours of hard laps on a road course. If Hughes knows how to properly cut the oil pump drive gear on the camshaft, you'll be fine.
What he said. If the engine was stock before, you should have a lot more space than that.

You can usually take up to 0.100" off a stock, uncut head, and more than that off the block, but you really need to know what you're starting out with on both sides. Otherwise your final SCR will be a total shot in the dark. Since the short block is already disassembled and you're not looking for a huge increase in SCR, I'd recommend waiting until you get the block back from the machine shop and checking the final deck height with one of your new pistons installed. (If you needed to increase your SCR so much that it required cutting a significant amount off the block AND head, then I'd reassemble one old piston/rod assembly into the block with your crank, and start with that measurement.)

Meanwhile, clean up all the combustion chambers in the head really well (I like Scotchbrite for this kind of thing) and measure their volumes with a combustion chamber measuring kit. The valves will need to be installed for this. A simple kit like this is all you need, so if you have a scrap of lexan and a 60 cc syringe you can save yourself $25. An uncut Slant 6 cylinder head will probably be somewhere in the 55-60 cc range for each cylinder. Use the average of all six for the following calculations; hopefully there's no more than a couple cc variation between cylinders.

Enter the above info, along with your final bore (3.460"), your stroke (4.125" for a 225), and typical numbers for a standard head gasket (3.5" bore diameter and ~0.040" compressed thickness) and plug them into a compression ratio calculator like this one. Piston dome volume is zero for flat pistons. This will give you your SCR before cutting the head. Play with the combustion chamber volume until you get the SCR you want (8.5 or whatever someone like Lou/Dart270 tells you to shoot for after looking at your camshaft specs). Take that difference in ccs and multiply it by 0.0067". That's how much you need to mill your head.



If all that is too much work and you're certain that both the block and head are uncut (you can check the block to see if the stamped numbers on the pad behind the alternator bracket are still there), then cut 0.060" off the head and be done with it. That'll probably get you into the 8.5-9 range, depending on manufacturing tolerances at Chrysler the week that engine came off the line.

Piston-to-deck clearance was minimal, probably only a couple thousandths before I tore it apart.

it had new bearings in it, and the crank was turned to 10 under, which could be why it was only intermittently knocking when I first started driving the car.

but it's not like I can't just pull the head at a later date and have it decked.

Did you find a bad bearing? Having it .010 would have nothing to do with the knock if the correct bearings were installed.
Just wait till the machining is done and install one piston assembly and measure the volume and get the head cut to what you need. No use to assemble and disassemble an engine and assemble again?? Unless you enjoy doing extra work!!

Thanks for posting that link to the Hughes cams. I see they have several grinds. That one is not aggressive. You can use it with a stock or mild stall converter, but I would not expect to get more than 200 HP, assuming you have a decently ported head. 200 HP in a car like yours will net something like mid 15s in the 1/4 mile, which is a good streetable number for these engines and it feels zippy on the street. Focus on good head porting and larger valves if you want to make power. If you can afford a 2600-3000 RPM stall converter, then get the 220/224 Hughes cam (if you want to stay with Hughes). I do not know if anyone has tried these who is a serious Slant enthusiast.

Lou

Alright, I'm trying to do a budget rebuild of my Duster's slant 6 and I'm trying to do it for a reasonable amount of money.

It's going to have the offenhauser intake off of Summit Racing (what would be a good 4bbl for this engine?) and the small tubular headers off of Aussiespeed.