Being have I own both, and a member of both types of forums, maybe I should start a war and put a link on both forums to see who comes in. HAHA.
Its alomst never a fair fight when you compare two car with only one having a poweradder. Hell I've even been beat by a Zx2 with a turbo, before in my farly modded 5.0 which has twice the cubes he did. You need a lot of extra cubic inches to make up for the poweradders.
Besides my 88lx I have a 71 dart with a 360 and it moves pretty well. As the cars are now. The stang can't keep up. The only thing that would seperate your car from his is the
vortech.
Now he was to spend $500 dollar to match your poweradder with nitrous you would be seeing taillight all day.
My 71 dart swinger has 750 demon cam, edelbrock heads, TTI headers, 4:30 gear, 3800 stall converter. I have yet to dyno the car but I have seen same combos in the high 380 area in power. I have run low 13's. Which would not be enough compared to your 512hp, But if you get a poweradder it is only far he bring one too.
Now about the weight of these cars. Not to many people are famiular with the darts. These are Chrylser's strip down, bone accentual, factory race cars. Made light and fast with large engines. I don't care what brand you love, ( my self am a mustang fan to hart) Some dart including mine came with no air, no radio, rollup windows. Hell the hemi darts came with straps attached to the window to lift them up or down. If you were smart enough to by one with a hemi back in the era, nothing would have keeped up. Hemi darts are legendary.
I know my 71dart wieghts less than my 88lx by a few hundred pounds.