I'd build the 543 but I wouldn't be building something for maximum hp. I'd rather build a BIG mild motor, no need for insane rpm no need for big compression. Just a big torque monster.

i wonder how something like that would react using a pair of long rams and a couple of the small thermo-quads ?

I just found an aluminum block! so lucked out. not going to take a chance probably build a 605 now.

i wonder how something like that would react using a pair of long rams and a couple of the small thermo-quads ?

Probably horribly

Actually they should really work nice. The only reason I didn't go that route was I didn't want to permanently alter a rare set of ShortRams.

I was thinking b1 heads have slick rick do them up. A uy contacted me about an iron block but I have no idea what it is? P5007628 made in canada by cummings said it has a 4.38 bore. not a bad price either $2,200.00

There are only 2 different manifolds, the more common Longram and the hp version the shortram. They both have the same length runners but the shortram has its runners only isolated from each other for about 12". The longrams have each runner isolated their intire length. On the 413 the Longram version was rated at 375hp&495ftlbs. The shortram motors depending on the year were rated at 390 or 400 hp and torque figures vary some literature stated 465ftlbs.
The Thermoquad carbs could be easily setup and tuned for these manifolds but I don't want to permanently alter a rare set of manifolds.
Nicks garage U-Tube channel did a 63' shortram motor for a customer but they either missed on the cam selection or installed it at the wrong centerline as all they got out of a 426ci motor was 375hp&501 ft lbs.. The shortram motors were very fussy on the installed centerline and the factory used a special cam timing gear 2° retarded.
My 446 Shortram motor made 429hp@5150&544ftlbs@3800, it made 512 ftlbs@2500. All the pulls on mine were made at 34° timing, in hindsight I should have bumped the timing a few more degrees. Also I didn't have a windage tray installed either. These 2 items should bump the hp&tq up a bit more.
While dyno testing the motor I tried an M-1 single plane, a Weiand Tunnelram, and the Shortrams, the Shortram manifolds made the least Hp but buried the other two with their torque curves. Installed in my W-150 the ShortRams have explosive response.