I recognize that car being from Huntsville, AL.
I'd swap for 300lb on the front, 250 on the rear due to the less effective mounting angle on the front. Looks like 10 inch springs. Measure installed, fully extended length without adjusting seats (full droop). Use spring closest to that length.
_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS
viewtopic.php?f=5&t=13225&p=134742Simple Spring select
viewtopic.php?f=5&t=11815LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12