Calvin,
The part # for the Schumacher straps is U744R. It comes with 2 complete straps which will do 1 car.
I probably made this sound harder than what it really is.
Countersunk screw holes require a tool which works with a power drill. Available at any Sears or a good hardware store like Ace.
If you want to make it easy...just use the slots(for the tape or velcro you already use). Use philips head screws and some washers to mount the new straps. That way you can adjust their position a little. Very easy. Its worth the $7.00 (approximate) investment.