My notes say 185 (calculated) on the seat with the 68380X2 spring:
https://www.jegs.com/i/Crower/258/68380X2-1/10002/-1#. I think the springs from Dave were around 150 and were fine.
I had this same top end package on my 464 till it spun another rod bearing. I ran great and was close to perfect with all kinds of power from about 2500 through 5500+ RPM but found myself going from no traction to needing to shift in an instant. I wanted the RPM range extended out and thought that I had no use for the brutal low end.
So I milled the heads .030, added the Crower springs, built a 433 and moved everything from the 464 to the 433. Don't get me wrong, the new motor is plenty fast across a broader RPM range. I added heavier wheels, larger rear discs, wider softer compound tires, lowered the rear significantly and changed my shock settings. Between everything, the 433 in the car as it is now is probably faster on the street than the 464 was but with the fuel injection and timing control, everything is more progressive and you don't get that explosion of torque that completely blows off the tires.
My main issue at this point is that the car actually drives quite normal and as such, I find myself wanting to just cruise it normally more which then puts me in OD a lot more and that is where the problem is. In OD I am usually at 1700 RPM or so which was fine with the 464. But with this engine the OF is not happy cruising around in that area under a light load. I'm going to try advancing it and playing with the tune a bit but suspect I am just trying to put a square peg in a round hole and at some point, will need a cam more suited to the way I actually drive the car now.