Depends on how you plan to drive it.
Putt around town and never get on the hwy, 4.10 will be ok.
Any hwy driving and they will be a disaster. No fun going 60 in the slow lane with the motor screaming and mini-vans blowing by.
The rebuild was the majority of that improvement.
People kill for 10% gain, you got over 50%, unheard of.
I gained 1-2mpg, went from 12 to 13-14 or so for the EFI only.
When I added OD that was a game changer, and that only gained 25%
Sounds like an intermittent problem, maybe heat related.
You change things and it works, not necessarily the part changed, maybe just cooling down.
I'd check and adjust the reluctor on the distributor, easy to do and doesn't cost anything.
I wouldn't trust Holley as far as I could bowl them.
They were bought by a private equity firm, and that never works out long term.
They've already cancelled many 3G parts that were just released a few years ago.
Good input about asking the OP what the goal is.
I did EFI on my 340 10yrs ago using FiTech system. Easy install and was big improvement over the carb. I didn’t know how, or the interest, in fiddling with the carb endlessly.
It wasn't cheap, as mentioned, you need to upgrade the tank and fuel...
If you're worried, add a toggle switch on the ground side, and put it under the dash.
Will act as a reminder, and also act as simple theft protection.
Car won't start unless you flip the switch to ground side.
Once started, you can flip it back, no harm when engine is running.
Yep, you can permanently ground the NSS wire.
Just be careful, engine will turn over in any gear.
Accidently left mine in drive, when I hit the key, it started and moved forward, luckily nothing in front.
Agreed, that's where I'd start.
Measure voltage to coil/ballast resistor while trying the key.
Disconnect connector on column and you can do it yourself.
Ignore stuff at bottom, that's for a 3G swap.