Hello! Those 2 combos would work fine, but I highly suggest this one. Its cheap and on sale.
http://www.atomikrc.com/collections/...ss-motor-combo
About the pinion problem; sorry, you can't use those. The one you had on there before should be fine, too. BUT, if you're 100% set on using them, you can get a bigger spur, but that would be counteracting the pinion change.