O.K. then ;
Go for a good used HEI dizzy complete with wires and everything , open the spark plugs up to .070" and watch it roar into life every time .
Or this :
http://www.ebay.com/itm/NEW-CHEVY-6-...9dfad9&vxp=mtr
Me , I more trust the old original stuff but sometimes the flyweights and bushings etc. need replacing , lucky for us GN used the same mechanical parts and module as the V-8 dizzy did .
Early 250's were set to 10* BTDC but by 1967 the smog tests mandated TDC timing , depending on your engine's health one or two degrees timing makes a
HUGE difference ~ if it cranks over fast & easily , I'd start with 10* and back it off one or two degrees at a time if it pings or diesels .
*DO* unplug that vacuum hose when it's hot idling to see if there's any vacuum signal .
Enjoy that
402 ! who's paying the fuel bills ?
.