Tossing Around 273 Ideas

I would not even bother with bigger valves with any first level boosted setup; it will indeed overcome the valve size, not any problem at all. I'd put my $$ into good forged pistons and good bottom end parts. Maybe 8:1 SCR (open chamber heads), then a good intercooler.

Why not go single turbo and keep it simpler? You're going to make plenty enough power to quickly find that traction on a Ram50 is going to be the main problem, not torque and power; 14-15 lbs boost will get you up into the 400+ HP range with 273 ci without hardly trying.

Draw through has the carb before the turbo, blow through has it after. Draw through means any carb is set up normally; blow through means it has to have items to make the carb pressures equalized to boost at places like the bowl vents and the fuel inlet, to keep the boost from blowing back out these points. Draw through puts the fuel air mixture through the compression process, with has some particular problems like cold starting and keeping the fuel in suspension throughout the long passage from carb to cylinders; blow through gets around those issues.