My 3L is a wood chassis and yours should be fine also. You would need to select the correct spring weight.
MARCOS
MODEL
YEAR
SPRING
KITS
PRICE
LOWERS
mm
mm
FRONT
DAMPER
PRICE
REAR
DAMPER
PRICE
ROADSPORT
KIT
PRICE
GTZ
KIT
PRICE
GTX
KIT
PRICE
Marcos
Coupe
64>81
PE529
£90.00
PE951
£90.00
Marcos
Mini
65>
TA236
£55.00
TA237
£55.00
Mantis
70>71
PG331
£90.00
PG332
£90.00
Mantual
(rear loop/loop)
89>
PE591
£90.00
PE592L/L
£90.00
Mantual
(rear loop/stem)
89>
PE951L/S
£90.00
This is from the AVO website under classic shocks.
Mark