1970 Duster, Trans-Am-inspired "Pro Touring" build
One tuning "mod" I did just a couple weeks ago was switching the vacuum advance from ported to manifold. The engine definitely likes it; it pulls harder from a stop with less throttle on light acceleration and runs a bit smoother, I could tell before when the throttle would close off the vacuum advance and it felt like the engine had to try harder, it's tough to describe. Anyway it works perfectly because with my cam and compression the engine pulls barely over 10" of vacuum at idle which isn't quite enough to pull in much vacuum advance but as soon as it get over 1500 RPM or so the vacuum comes up rapidly so when I decelerate or just barely crack the throttle when the car is moving the extra advance is still there. I'm also going to pull the distributor and redo the springs to bring the mechanical advance in earlier. Right now it's all in around 2500 RPM which works fine with my 2600-stall converter, IF I'm flooring it. If I'm not at WOT from a standstill the RPMs don't go that high and I think it would run better with the advance all in say around 2000 RPM instead.
Overall it runs like a champ, can't say enough good things about junkyard 5.9L Magnum short blocks. I have maybe 5000 miles on the engine now and aside from a little oil burning from the valve guides on startup after it's been sitting a while the engine is "tight". Performance is excellent and while more compression would be better it still runs DAMN good the way it is now and it's nice being able to run regular gas. Especially when it averages 13-16 MPG lol.