what is the biggest diesel engine i can put in a 1985 f150

https://www.hotrod.com/articles/ccrp-0602-big-block-ford-engine-build/

The 460 is an alternative if you want gas power. If you want a hot rod 500hp is an easy build.

thanks i might go with the 7.3 and do the suspension and frame work i want something with high towing power and a beast offroad

Save money, time and get it done right by buying a 3/4 ton (or 1 ton) truck with the diesel!

You do not need super high HP when offroading, just the right gears. A mild build of a gas 460 will get you over 500 foot pounds of torque which will exceed the torque of a stock 7.3.

BTW. You want a Powerstroke 7.3 which came out in 94, not the earlier 7.3 engine!

ok thanks hey do you know where i can get any cheap tires

You can probably find a used set on Craig's List. New tire prices are more or less the same where ever you go.

ok