engine builup basis

hi!
after getting a lot of precious advice for my engine buildup(especially regarding strenght)i come up with another question:what displacement?
engine is still based on a production mopar cast iron 383 "b"(low deck) big block (4.280 bore),methanol burning bird catcher and HH 8.71 khul blower.rods are 6.525 long alum BME units.these are the things i have.
i have 3 stroke options,hence my question.
from a calculator,got the following input:
stroke: 3.75 3.90 4.15
bore: 4.280 same
deck: 9.98 same
rod: 6.525 same
chamber
volume: 88 same
gasket
thickness:0.06 0.02 0.06
piston
dome: 12 0 0
pin
height: 1.58 1.50 1.38
deck
clearance: 0 0.005 0
CR: 10.81 10.8 10.58
CUI: 431..6 448.9 477.7
rod ratio: 1.74 1.67 1.57
max rod
angle: 16.7 17.39 18.54

was told that rod ratios and angles had to be taken into account:how?
pistons will be custom made.
then i got that info,for 7000 rpm max:

mean piston
speed(fps):72.9 75.8 80.7
peak piston
speed: 114.5 119.1 126.8
peak
accel: 3357g 3522g 3803g


how does all these infos affect my choice?
target HP 900,for a small wheelbase funny (100 in) and auto trans
any help greatly appreciated!