a new 48* Tall R3 is as close as your nearest MP dealer....

4.185" bore, R3 Callies 4.0" Crank..... 439 inches....

Will need good rods, ie. Oliver/Dyers/Carrillo etc I'd run a 6.20"

Custom Pistons.... ~28 CC dish with a 68 CC INDY chamber would be ~9.5:1

Set of 230 CNC Oval INDY's

Solid roller in the 256 @ .050" range, .650's lift on 114ish LSA.

INDY manifold, blow though 950 C&S/ CSU/ Pro Systems

Borg Warner S480 single 80 MM..... easy 1000+ HP & very driveable/mild.