So, it's kinda an odd build but it will do what you want. Like a tractor motor sorta. 540 cubic inches, that cam, those heads and intake......your rpm of peak horsepower will be about 4,200 rpm. Let's look at the bright side.... with a 4.5" arm you may have 700 lb-ft of torque right there. 2.40 rear end gears, 28" tire and you may go 160mph
Let's keep all your pieces. The lifters you have choosen will need adjustable valve train as stated in the Comp Cams catalog.
I love the 850 Mighty Demon, should work until the heads give out.
You might get lucky and squeeze the long arm by the oil pickup boss in the block.....but figure on contacting Milodon and getting an external oiling system.
Best of luck.
