360 or 440 for my 1970 dart daily driver

Hope you the best bad timing just don't get yourself in a situation that gets out of control - Go small block my combination is a mid range built 360 - Doug's headers - Fitech EFI - 833 manual 4 speed - 3:55 gears - HDK tubular K member with coil overs - Air Conditioning it's a fun car that does several thing very good nothings cheap to do took me many years to get this car where I like it -- doing and redoing -- good luck and I hope I made a point that sticks with you
Mileage wise what does this combo get you?