I use schrader valves
(car style) in preference to Presta as they're a much better fit in the larger GM valve holes.
A schrader valve also allows you to easily remove the valve core to enable
slime sealant to be pumped into the tube to give better long-term protection against punctures and slow air leakage.
With the deep "V" GM rims, a longer stem is always preferable to a short one, as it is better to have too much valve protruding from the rim than too little.
I have used shorter 40mm schrader valves but they can be very difficult to inflate from flat as they will easily push back into the rim.
I would always use a screw on extension to prevent this from happening and then remove it once the tyre had been properly inflated to hold the valve in its correct position.
Check out
this video for more information on inner tubes.
Alan