new to me engine - what to do with it ?

do you have a tach in it? does it rev at least to the 5k your cam card calls for smoothly?

if not i'd think about swapping for a known, good ignition box...the mopar units have never impressed me. I had 2 Mopar boxes only letting my first engine (also a 318) rev to 4000. Threw in a MSD box and it would rev to 6K. Not saying you need to go as far as an MSD box...but at least worth swapping for a known working unit. @ 3700 lbs you surely aren't the heaviest thing on the road, but it is some weight to lug around. The heads are probably a bit much for a mild cam 318, but mopar heads don't exactly flow to the moon in stock form so i don't think they are killing you.

I'd maybe borrow and test another carb, box, and check your timing. If neither of these really wake it up, maybe it's all it has.

I'd buy a test n tune ticket when the tracks open up for $20 and take it down the quarter mile.
@ 3700 lbs, and hoping that engine makes what? 250 HP? you should be well into the 15's

if you run a 18.00....you're making approx 150 crank.

check this link out for giggles

I had an old K10, with a bone stock 305 that ran 18.00 and that engine was 160 rated from the factory, and it was probably 4000 lbs. surely i'd hope you did better than that sled!