I KNEW there was one out there. Right Stuff Detailing (
www.getdiscbrakes.com) lists PN CIN7104 as the front-to-rear brakeline for a 71-72 Chevelle 4dr. Note that while the do not list one for a Cutlass 4dr, the 2dr Chevelle and 2dr Cutlass both use PN CIN7131. While there's no guarantee, I've got $10 that says CIN7104 fits you 4dr Cutlass.
By the way, they also list the front-to-back main fuel line for the 4dr as GCL7104. Unfortunately, the do not list a return or vent line for that application. Good luck.