Cranks but won’t start

[Fbks_Cruiser]

350, HEI, edelbrock 1406.

Truck has always started easily. Press pedal once to set choke, crank a second or two and she fired right up. In colder weather 2 pedal pumps. Then Last week I had to crank for several seconds before it would start. But then it ran good, started fine and started fine the rest of that day.

Now today I jumped in the truck press pedal to set choke and crank away but it never fires. I press pedal again. Still cranks but no fire. Pedal full to floor no fire.
So I pull the air cleaner, open choke butterfly and work the throttle, see good fuel spray. I then check power at HEI 12.5 volts key on (12 gage wire from ign unfused). I do note that voltage drops to about 10v when cranking, too low?
I tried a ignition tester that goes inline between spark plug and wire, showed a flash as I cranked the engine so it appears I am getting fire to the plugs.

I had a spare ignition module and coil so I swapped em just to rule that out. Same symptoms.

If I hold pedal to floor and crank a long time I get occasional pop out the exhaust, so I am thinking timing is goofed up? But how? It ran great when I parked it last week.

Ideas?