Welcome @cloud51ve!
looks like you’ve hit your post limit. one of the mods will be by soon to
remedy this for you.
@anorak234 @BillGordon @Dareno @jamie @mmaner @Sender @Zach
in the meantime i’ll provide my opinion on your questions but please seek out input from others to get a balanced perspective.
this is a super fun space to DIY but know that it is unlikely to be less expensive than an off the shelf board or kit. take a look at build kit boards or similar for reliable and cost effective set up.
these are good things to consider when starting a build, something that is not intuitive is the enclosure. I see you are a mechanic so its possible you are learned in the ways of fabrication, if this is not the case you should choose a deck that can easily acomodate an enclosure off the shelf
Midlength: 36- 39"? rider height and riding style would be helpful to know
lots of power: you will not be disappointed with 6384 170-190kv motors use pulley ratio to adjust speed/torque.
battery pack: depends on your goal. many will tell you “higher voltage = faster” while this is true it should also be noted that higher voltage will run cooler. 10-12s are quite common with 12s increasing in popularity in last few years.
ESC: you state “high constant amperage” but do not define, in general assume less than (40)A per ESC V4 will work well, (50)a greater per ESC look to V6. flipsky can be hit or miss on quality.
Wheels “90mm wheels” good size, make sure the core will work with your pulley system, Kegel (circles) and Abec (slots) are both popular.
Dont forget remote, enclosure, telemetry, and safety gear.
few of us are, just be thankful you arent as ugly as @BillGordon or @wandagoner - on their best days they make Marty Feldman look like a square jawed quarterback with time and testosterone to spare.