I think those gloves are already ingame, try downloading simple native trainer to switch to them (not sure how you'd get them without cheating
I'd advice you to carefully read the readme since it gives instructions on which other files you need (and provides links). I believe it's somewhere on the bottom (the first few pages are just functions of the trainer).
Press F3 to launch it ingame, then use numpad to scroll through it. Not sure what the exact title was but one of the items on the list should give you access to niko's clothes. On hands you can change it to 2 and it should be those fingerless gloves.
As for cars, to save yourself alot of trouble I'd just stick to the cars they are meant to replace. Do keep in mind that installing custom cars causes the taxibug which is a hard thing to fix (just google it).