New fella sweet truck!

[Craig Nedrow]

Welcome, that holly has a mechanical choke but no cable to it, so basically not being used. Two things you can do. 1) get a sheathed choke cable and install through the firewall, and attach it to the choke mechanism, 2) buy an electric chile from holly and install that. I much preferential method two.
I love the adjustability of the holly, and how easy they are to work. Having said that, get a good holly book. If you stay with the carb, you will probably need to adj the jetting.

 

[Craig Nedrow]

Welcome, that holly has a mechanical choke but no cable to it, so basically not being used. Two things you can do. 1) get a sheathed choke cable and install through the firewall, and attach it to the choke mechanism, 2) buy an electric chile from holly and install that. I much preferential method two.
I love the adjustability of the holly, and how easy they are to work. Having said that, get a good holly book. If you stay with the carb, you will probably need to adj the jetting.

https://www.gmsquarebody.com/threads/1973-k20-350-to-454-swap.29840/page-8

This shows how I used a a/f gage to tune my holly

 

[malibuman402]

Welcome from NC

 

[Long Rider]

There should be a choke on the opposite side of the throttle linkage. I can't see either in your photo. Welcome aboard from eastern Oregon

 

[Grit dog]

Welcome, that holly has a mechanical choke but no cable to it, so basically not being used. Two things you can do. 1) get a sheathed choke cable and install through the firewall, and attach it to the choke mechanism, 2) buy an electric chile from holly and install that. I much preferential method two.
I love the adjustability of the holly, and how easy they are to work. Having said that, get a good holly book. If you stay with the carb, you will probably need to adj the jetting.

https://www.gmsquarebody.com/threads/1973-k20-350-to-454-swap.29840/page-8

This shows how I used a a/f gage to tune my holly

I might not install a chile lol, but OP should install a choke for sure. Good that you saw that.
Maybe keep OP from beating on his engine like he is.

 

[86 C10 Shortbed]

Welcome from Central Ohio

 

[Oliver]

Symptoms sound like a possible vacuum leak. Put a vac gauge on it, spray some starting fluid of flammable brake clean at base of carb and base on intake manifold. If engine revs up and vac gets higher, you found the problem. Do not over do the flammable stuff around electrical or exhaust manifold. You might need fire insurance if you do!

 

[mrfleet12]

Welcome from Illinois, new to the site myself after recently acquiring an 84 SB.