Will not stay running.

I have recently received a 1972, yes that year is correct, GMC 1/2 ton with the original 350 4 barrel, column shift. My plans will be to restore it back to as close to original as I can but I also must drive it for everyday usages. Heres the problem with that; it only runs when it is cold. As soon as the choke opens it will not hold an idle unless by force; and then when I do force it, which cannot be good, it drags and jugs at half power.
When it is cool it has lots of power with no hesitations but the moment the choke is open, whamo nothing until it sits for several hours, overnight actually.
Where would be the best place to look for such a wierd thing happening.

Thanks; sorry I cannot pay you for an answer at this time, payday is not until Wednesday and my CC will bounce until.