'
Comparing w/ other Blackjack/Appliance Headers, they appear more Camaro like than 'Velle?
1'st pic below is your pipes compared w/ Nos '68-72 Velle pipes from this thread, note swept back angle of mid runners...
https://www.yenko.net/forum/showthread.php?p=1301952
2'nd pic is yours compared to 1'st Gen Pipes from this second linked thread, pass' side looks different for accessories perhaps but driver's almost the same other than pic angle?...
https://www.yenko.net/forum/showthread.php?p=1260298
Also of note in the second linked thread is Member Whitetop mentions he has a Blackjack Catalogue.
Best of luck!
~ Pete
.