I did the same change to my Lebaron. went from 3.900 stroke to 4.25 stroke, and another .005 on the bore. And of course the crank, rods, and pistons all new. I used the same World block, Indy SR heads, Indy intake and Racer Brown solid lifter camshaft. CR went from 13.5 to 1, to 14 to 1. Dome much smaller on the 512. Quickest pass with 469 c.i. engine was 5.53 at 123, and at 512 c.i. it went 5.45 at almost 126mph. I did try switching from a 1050 carb to an 1150 on the last race of this year and went 128 mph but slower. Only one pass then I switched back to the 1050, and was .09 quicker and 4 mph slower. Same 1.21 60ft. Something not right in the middle but did not have the time to tune, so I switched to the tried and proven 1050 so I could have a chance at winning some cash. I did get to 4 cars on sat. and a R/U on sunday in FB class at Holly Springs thanksgiving weekend.