did someone call?
cheers rodger me ode!
right, so you're sticking with the stock manifold yeah? and you want a free flow system, no cat, from the manifold single pipe join to the exit, with more of the italian song, not neccessarily too loud, sound about right?
and finally, you have a series 2 1712cc 8valve on the stock carbs, yeah?
well, for a stock motor, you won't need anything bigger than 2", 2.25" maximum, anymore is pointless and you can start going backwards (not literally! ha ha!) plus these sizes are quite easy to scale up to from your manifold without ridiculous steps.
for a good sound, and quite a bit of noise, you can pipe straight through to a single resonator box at the back,
this was my own 33 16v with a crossover manifold, which is why is sounds a bit different, but just a single oval resonator at the back, approximately 8" wide x 15" long, and out to a 2.5" rolled back tip.
My Alfa 33 1.7 16V with PetrolHeadParts Crossover and System - YouTube
it came up at around 93 db maximum, but you do have to take a bit off, because at the time my waterpump which you can hear was probably responsible for a few of them!!!
if you built this sort of system first, and found it too loud, which i don't think you would really, you can always add a small round resonator for a centre box in place of some of the straight tube.
how does that sound for a plan so far?