Scott,
A Weber DCO series carb is very cool but overkill for a stock engine. It's not easy to dial in but once done, it's great. No real HP gains though. The Weber downdraft is OK but I generally remove it and return the car to SU's. The stock SU's are very good carbs. Once set, leave them alone. If the engine starts running poorly, check compression, point gap and timing. The carb adjustments do NOT move, so no need to adjust them.
Here is my suggestions for a great running street car that you won't have you under the bonnet all the time. There are more parts to the car than the engine to fail, so there is more to do. I'm only going to deal with a tune-up here. You should, actually must, have a workshop manual to continue.
1 - Engine must have even compression, good oil pressure, no vacuum
leaks, new belt(s) and hoses, thermostat, clean radiator
yada yada yada
2 - Adjust the valves per the manual
3 - If installed, insure the smog equipment is correctly configured and
completely operational. If removed, insure that all the connections
are correctly terminated
4 - Be sure the distributor mechanical advance is free and lubed
5 - Be sure the distributor vacuum advance is operational and the line is
insatlled and open.
6 - Install a Pertronix ignition module in the distributor
7 - Install a new distributor cap and rotor
8 - Install new spark plugs, correct heat range, and wires.
I use NGK BP6ES plugs
9 - Insure the coil and connections are good, no cracks or leaks.
10- Set the timing statically
11- Install an in-line fuel filter at the tank before the fuel pump.
12- Replace the points style fuel pump with a new SU solid state pump
13- Rebuild the carbs, insure the throttle shafts don't leak and that
the needle and jet are replaced, using the correct needle. Also
insure that the N&S are replaced and the float level is correctly set.
14- Preinstall a pair of K&N air filters, oiling them first. Set aside
Assuming you have a manual for the car, preset the carb jets and idle screws per the manual. Start the engine and let it warm to operating temperature. You may have to screw in the idle jets some to get it to "idle". Using a timing light, set the timing per the manual and then rev the motor slowly to ~3000RPM and insure the timing advances smoothly. If all that is good, set the carbs per the book, install the air filters and go for a drive. Pretty easy, yes?
DISCLAIMER:
1/ If any of the above suggestions are not followed, all bets are off as to your success.
2/ This is an armchair instruction, aka from a distance, and all the variables are unable to be identified and discussed. The workshop manual is an invaluable tool, as is common sense. Don't do anything that doesn't make sense, don't use unneccesary force and think everything through before attempting an operation.
3/ I have no responsibilty, express nor implied, for the operation of, maintenance of, repair of or any factors not mentioned for any motor vehicle that I have not personally and physically been involved with and no consideration has been exchanged.
Good luck and keep the shiny side up.