Baffled!! The truck won't fire.

[bessie66]

Hey everybody!, here's the deal;

'71 C10 2wd 350 w/ Hedman's, Performer Intake and rebuilt 1405 600 carb spreadbore adapter(both Eddys)
New distributor. I installed new plugs today(ngk 3442 i have ran for the last year) to try to fix the no-start issue.

Truck has been running with this combination no less than a week ago, but at the moment it will not start. I've researched this topic, like most, a gazillion times...

This is not my first go-around with a sbc, and I have done everything but a leak-down test but may have missed something simple... I'm baffle because it went from running to nothing, for no apparent reason - literally ran the night before, nothing the next day. The motor cranks and sometimes sputters(every 4 cranks or so), but no go. The carb is squirting healthily and obviously there's spark to sputter. From experience I've put new plugs in and sh*t fires right up. The plugs I removed appeared fouled. Ripping my hair out. suggestions and/or theories of any kind welcome!