It's never going to be fast (especially shifting a truck tranny) - but if it is a stock original engine (327, 350 not a 307), and you want a little street cred, some fun, and some sound without killing the street performance..........
If it has an original QJet - keep it and put on a spread bore manifold like an Edelbrock Performer 2101. Even has provisions for the factory choke on that manifold. Q-jet is plenty big enough and a decent carb for economy. Don't forget some pretty valve covers, and a re-curved HEI distributor. 1 5/8" full length tube headers, with 2.5" exhaust run out the back or in front of the rear wheels.
If not original Qjet, I vote for a square flange dual plane intake of which you have countless choices, and a 650 Holley VS.
You may want to keep that original camshaft, as there is little for you to gain in the torque dept without good heads, and a 1969 is not a big emissions engine.
But if you just have to have some lope at idle, pretty much anyone's flat tappet hydraulic somewhere around 270 degrees advertised duration and 110 LCA should get you there. But there will be a price to pay for it with a risk of failed break-in, lower torque at low RPM, poorer fuel mileage, and a need for upgraded valve springs if you're going to get over 5000 rpm.
A nice 69 4x4 is a VERY desirable truck - worth a lot of bucks - that in itself is cool! Put some trim ring wheels with some wider truck tires (not tall - my personal preference) along with the intake and headers and you'll be all set! Don't loose any of the original pieces that you take off.
Best wishes
