I've never had the car up past 35 - the old nylon timing gear gave out before I got past the initial shakedown phase. Ultimately I'll probably have the car geared on the low side when I get an 8.75 rear end.
One last question on the 252H - it says I need different valve springs, but I can't find the needed springs listed anywhere? Were the stock valve springs really that marginal that they need an upgrade even with a mild cam?