Miles/gallon: Newer vs Older Cars

I built a really low buck,low compression 360 67 'Cuda,...Put in the basic 3:55 ,Road Runner converter set up...,set it up,mild RV cam,headers ,bla,bla, Sold it,some one took the time,to tune a late model smog Thermo Quad,and curve the distributor. It passed California smog specs,at 25 ppm,.02 C0,cleaned to 7 ppm h.c.,.01 CO ,@ 2500... It went 13.60's as a best,13:80's at California
,87 pee water fuel .727 trans,it got 20-22 mpg at freeway speeds. I LOVE od transmission's,s sometimes it's not in the budget. 83 Mustang GLX,5.0 ragtop: 3:73 rear end,stock 83 T.5 transmission,basic 5.0 carbed,with the good Edelbrock intake,the usual 204,214 @ 050 cam. It got 26 mpg,with a 4010 Holley double pumper..New cars,are nice.. not necessarily worth that monthly payment.