Pulling my hair out with the ignition system I inherited with my project - hodgepodge of Mallory dual point, CD blaster coil with resistor. So I'm thinking going old school and dropping in a Dura-Spark setup. Local boneyard has one complete from an 89 5.0 - distributor, coil and module. Will that work on my carbed engine? I've read that I need one from '75-'85 date range. Thanks!

 

Ford 302/5.0l distributors are compatible from 1969 and up.

While Duraspark is OK you really want to use an HEI system, more reliable than Duraspark and less expensive.
Chevy doesn't do many things right but they hit one out of the park with HEI system

1 wire hook up, 2 wires if you want a Tachometer

You can buy 302/5.0l HEI distributor as one unit, $140 summit, Coil on cap with module, plug n' play

Or you can use Duraspark distributor and coil, and use HEI module($30) instead of Duraspark module
Google: duraspark HEI conversion

 

RonD, you are the go-to guy! Too focused on the Dura-Spark and didn't look much at the alternatives. The Summit unit costs no more then the boneyard. Great pick, thanks!
The reason for the distributor is that I've been having carb tuning issues. The truck came with a new Demon with nasty off idle transition issues and raggedy acceleration. So I rebuilt a Holley 4160 that's been laying on a shelf and got exactly the same issues (good vacuum by the way). I knew the points were ratty and who knows about the choice of coil. As they say, 95% of carburetion problems are ignition, so I'm trying that out. Thanks!

 

Good choice
Back when I was doing restorations I put in HEI(coil in cap) distributors on pretty much every engine, they came out in 1974, most restorations were mid-late '60's models, loved those old 'muscle' cars.
Put original ignition parts in a box and sold it with the car, original equipment is great, but driving the car is GREATER, lol

Look at Ported vs Manifold vacuum for spark advance each has its good and bad points and each has it's own adjustment setting once you decide on one or the other.
Ford also had an interesting setup for this, a heat controlled vacuum switch.
Unit had 3 vacuum ports, and screwed into a coolant passage like a temp sender.
It would switch distributor advance from ported to manifold based on engine temp.

Basically spark timing sets when full combustion takes place in a cylinder.
You want that to occur about 10-15degrees After TDC when piston and rod has the best leverage to push down on crank to add power, too soon and no leverage, too late and full power of expanding gases isn't used up
And Full combustion doesn't happen when spark plug sparks, there is millisecond delays as the flame front spreads.
And Rich mixture spreads faster than leaner
You also have RPM, obviously the faster the RPM the less time there is from 10deg BTDC to 10deg ATDC

Inside distributors are weights and springs, these change timing based on RPMs.
Just using these the engine will be sluggish, so vacuum(throttle position) advance was added, this changes spark timing quickly in response to driver input, gas pedal.
Like accelerator pump in carb adds more fuel quickly for acceleration

I know enough to get myself into trouble, lol, but not enough to tell you what to set it up as.
Poor spark timing can cause pinging/knocking, lower power, and overheating, good spark timing can squeeze more power from an engine

 

Interim fix: the setup I got was a Mallory dual point fed by an HEI coil with ballast, which didn't seem right. The box of parts the truck came with contained a brand new MSD Blaster coil. Hmm, says I, wonder what would happen if.... Bam! Nice idle, smooth transition and hiccup-free run up. Still going for the HEI, but nice to know I don't have to R&R the intake manifold or worse. Thanks!

 

Thanks for the update

Wonder why they had the ballast resistor on there?
HEI coil wouldn't need it

Older coils used ballast resistor(or resistor wire) to limit voltage at coil while engine was running, less powerful spark but made older coils last longer.

Newer coils have current limiting built in, so adding the ballast resistor could/would reduce spark voltage, which could cause the rough idle