try
http://www.webercarbsdirect.com/?source=overture
Myself with my datsun truck I put a bigger cam and I didnt jet my carb at all seems fine to me. Dyno would be a true way to go but as most I dont have in back yard
But most are like 130-140 main jet 50-60 idle jet and 50 on the accelerator pump jet I forgot the air jets cals myself.
No I didnt get huge HP improvements. But was noticable(But maybe cause it was a new motor)
I went from a 390 lift 248dur to a 460"lift 260dur and bigger valves
Port out where the weber fits thru the carb/adapter /manifold. So its a smaooth flow. no edges or blockage
Ck out the Holden Gemini site in Australia.They really pump up those Isuzu motors there
http://www.autopart.com/scripts/bckarn/parts.idc