Classic/Antique Car Repair: power 1976 chrysler ny brougham, vacuum meter, manifold vacuum

Question
Hard to get above 35mph. In park engine can rev up, in gear it trys to bog when approaching 35 and above.  The car starts easy. Put it in gear,okay. I've replaced all vac lines, except for brake booster line.
Replaced choke, rebuilt carb., replaced fuel pump, plugs and wires. Brake light is also on now. Brakes are fine. It has 440 engine. everything is stock. Hope you can help.

Answer
Well as difficult it is for me to realize that catalytic converters are found on old/antique/classic cars. I would suggest that you check the cat to make sure that it is not clogged as that what it sounds like. The factory manuals in the era suggested taking off the cat and installing a test pipe and road testing the car. It was not long before we discovered that using a vacuum meter connected to the intake manifold would give an indication that the cat was plugged. As the exhaust has difficulty getting out of the engine intake manifold vacuum will drop.
Brad