Like Curt said, extend the tubes 3/4" but I've no idea of your metal working skills and some are required to do it this way. 24" wheel and a wide tire is a simple way that's quick, clean but not free. Don't grind the fork tubes they are really thin wall tubing & safety is always top priority.
If you decide to go the tire wheel change out you might consider using a 24" front electric motor hub, that really simplifies the motor and drive setup 350 to 500 watt 36 volt will roll you faster than I'd want to go on your trike 20 + mph easy...don't get me wrong I love the idea of gas powered it's just a lot more work to get rolling and keep rolling.
The step plates I remember would require a bead roller and some sheet metal skills to duplicate. If you can settle for "in the spirit of" a pedal trike... treadplate or expanded metal on a metal frame both cut to the appropriate shape and size can be considered. I've built some pretty complex shapes using 1"x I/8" strap steel shaped around wooden forms. Then tacking the top (step plate) to the strap frame & then removing the wood form. Easier to do than to describe however, if you have some metal working skills.
Is the "trike section steel"? If so attaching the step platform is also somewhat simplified...I've found not many feel confident nor have the equipment to properly weld aluminum.
Rick C.