what kinof o gas milage can i expect from a 1975 valient with a slant 6. all stock running good? thanks

Lotta veriables,
should be mid to high 20's.
have seen much worse and a little better.
you are gonna want to put the tallest
15" tires you can get under it.
Just remember you can buy a lot of gas
for the cost of a new car.

nice i was hoping for at least low 20's. im good with keeping my foot out of the throttel so that should help and i may try to build an od tranny for it.

I've had a few, none did that much better than a 318 in the same (A) body if there was much stop & go. As suggested, keeping the RPM down helps, as does driving it for mileage instead of like, say, a rental car...
The 170 we had in our '60 Valiant (stick) got much better MPG than the 225 I had in a '73 Dart (auto), which of course was much heavier and had more (Calif) anti-smog stuff. The Dart got about 18 MPG overall if I remember correctly, 50/50 mix highway and street. A '75 is almost certainly heavier due to bigger bumpers.

I had a 74 Dart with a 225/auto. Got a best of 25mpg on the highway. However at least one piston had such bad blowby that the pcv air breather was gushing fumes INTO the air cleaner and clean oil would be dirty by the end of the week. But that thing just kept on going and did not too bad on fuel all things considered. Also I never did plugs, air filter, wires, or any of the maintinance items other than an oil change.

low mid 20's is about the best you can expect unless its one of the cars with an A833OD and 2.xx rear gears then you may get upper 20's but you will be out accelerated by kids on bicyles.

I got 19-20 around town and 22-23 on the hiway with a built up \6 in front of a A833OD and 3.55 gears.