Howdy Slick:
It sounds like your squeeze's ride has a mix and match engine. That's not bad, sorta typical on 45 year old vehicles.
The first thing you need to do is to verify what you have.
For example, the carb on a C9xx head, stock, would be a down-sized Autolite 1100 with no Spark Control Valve for the stock '69 distributor. BUT, the D1xx block would have to have an early, vacuum advance only, Load-a-Matic distributor. The '69 carb, with no Spark Control Valve, is not compatible with the '61 block casting distributor. So, what carb do you have?
Another concern I would have is that the '69 head was added using a composite type head gasket that is about twice as thick as the OEM steel shim type gasket. If that difference was not compensated for by milling the engine has lost about a half a point of CR. If you look carefully at the mating seal you may be able to tell what gasket is in place. It is nearly impossible to tell if or how much milling took place without measuring the chamber volume. The good news is that the '69 "J" casting gives the engine bigger intake and exhaust valves and a larger volume intake tract.
With a '61 block you will have a solid lifter engine. Hydraulic lifter blocks did not appear until '65, along with an upgraded distributor and oil pump drive shaft of off the bottom of the distributor. The '61 head would have had adjustible rockers to adjust the solid lifter valve lash. A '69 block would have had hydraulic lifters and the head would have had non-adjustible rockers to go with them. What does your engine have? The adjustible rockers from a '61 head could, and should, have been added to the '69 head when added to a '61 block.
So, to answer your question, "What should I add for a little more of an up dated performance without doing anything to major?", I repeat, assess what you have. If the '69 head came complete with exhaust manifold, that is a good 1st step.
The '69 exhaust manifold is a good upgrade over a '61 exhaust manifold. It will have a 2" outlet and a donut type gasket to the headpipe. A 2" exhaust system through a turbo type muffler would be a good 1st step.
2nd would be to make sure your carb and distributor are compatible and working correctly. Make sure the carb is achieving wide open when the gas pedal is floored. IF not adjust the linkage to achieve it. Add an additional 5 degrees of initial advance to the stock specification.
May I repeat- assess what you have and report back for a more specific list of minor performance enhancements. Reading past posts here is also very good.
What tranny? Rear gear?
Adios, David
