Got D44 1/2ton brakes, now pedal goes nearly to floor, bigger MC the solution??

I just finished swapping my Waggy D44 upfront with Chevy outers/brakes. They stop great, I never could chirp a 33 with my d30 if I tried and I accidentally chirped them a couple times with this.

The problem is that the brake pedal goes almost all the way to the floor before they start grabbing. (I know I bled them properly). This is because they need more fluid moving right? And the solution to that is a larger Master Cylinder right? And the E-350 MC is a direct bolt up on an '88 (besides enlarging some holes) right?

thanks

(I tried searching, but couldn't figure out any search words that didn't either get me nothing or way too much not relating to this)

Yes, a larger MC has more reserve volume, but you need to make sure the excessive fluid consumption is not from poorly adjusted rear wheel shoes/cylinders or other slack or air in the system.

Bleed, bleed and bleed again. You would be surprised at how much air is in the system in the form of small bubbles. Also, make sure your bleed valve is at the very top of the caliper and not letting any pockets of air sit on top. Rapping the caliper with a wrech helps get any spare bubbles to the top.

I FINALLY have decent pedal with my swap. I have 1 ton dual pistons on the front 60 and 3/4 ton GM single piston calipers on the rear. I am using stock 97 MC and booster.