79 crossle suspension swap help

Hello gents, I'm pretty new to ff and am currently engineering a 79 crossle for a friend in the valley of the sun. Were currently running Penske 8760 3 way adjustables, but for the championships at cota we need to be running straight body shocks. Were at 400f and 350r, driver would like to be at 350f and 300 rear, but for these, would the same spring rate be ok in the straight bodies be ok, or will the dampening and rebound in a straight body shock make those rates feel any different? Also if I could get a line on someone who's selling some straight body shocks, total length rear 13.25, spring ID, 2.5 5" free spring length(rear) 11.25 total length, 4" free spring height 2.5" ID(front) I'd be very appreciated. Also would be willing to hear from anyone with a cash+trade offer. Thank you