This is what I used.
EDGE INDUSTRIAL 5/8" Hose ID to 3/4" Male NPT MNPT Straight Brass Fitting Fuel
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I also installed a spacer i picked up from home depot to put inside the heater hose to block some of the flow like stock. I used a Hose clamp to keep it in place.
Hillman 1/4-in I.D. x 5/8-in O.D. x 3/8-in Long Natural Nylon Spacers