The OE spring for aggressive street driving with a BB was the XHD spring. Re-pops are available from Mancini, Firm Feel and others. In terms of spring rate, standard springs were about 120#/in and XHD was 140#/in. The XHD's have moderate arch as manufactured and seem to sag a bit with use so they tend to be low. I've got a set on an E and had an extra leaf added to bring the spring rate up to around 170#/in and get the height right. They are now a good match with 1" front TB's.

The other choice is to call ESPO (Springs and Things) and have them make you a set.

The same springs should mount on a D60 and 8.75.