[Espeefan]

For drilling holes in aluminum, you need nothing to extravagant. I wouldn't worry much about the length either, but a short drill bit will prevent deflection, while drilling, helping to make your holes a little more accurate. The bit will want to 'walk' a little, when you start drilling, so be sure you have some way of keeping the bit in place. A center punch might help, or if you intend to lay the old frame rails over the new, and clamp them togther, that should act as a good guide.

For a drill bit, get yourself any jobbers length, right hand, high speed steel, TiN coated bit in 2.5mm.

For the tap, get a spiral point, vanadium steel, nitride treated, right hand 3x.5mm size. The nitride treated tap will work better in aluminum, since aluminum is a non-ferrous metal. That is a metal containing no iron.

Other taps might want to load up with the aluminum, which will plug the tap up, and then when you back the tap out, it will destroy the threads. Aluminum will gall and stick to the tap flutes. I've had better luck with the nitride coated taps.

Make sure you get a couple taps, a tap wrench, to hold the tap, and get some thread cutting oil. You might be able to get away with chucking the tap into a cordless drill and using that instead of a tap wrench. The frames are pretty thin, so it shouldn't be a problem. Run the drill in low gear, and run it very slow, with oil on the tap. Or if you aren't comfortable, use a tap wrench and do it by hand. Probably safer that way.

Blow or brush off the chips, before you back the tap out of the frame rails, after tapping is complete. Clean the tap again before you start a new hole, and always put a few drops of oil on the tap. When you are all done tapping, blow all the holes in the frame rails out with compressed air, or flush them with a can of brake cleaner, or electrical cleaner. It gets all the metal shavings out.