The stock driveshaft can be reused--it just needs a 1350 yoke instead of the 1310 yoke it has now. Just have a new yoke welded on to the new correct length. A local driveshaft shop should be able to cut, weld new yoke, and balance for about $90.

The trucks who run 80e trannys usually don't have to worry about it being 'gutless' at launch. No need to worry about it man. I know what you are thinking and it won't be an issue. Just go ahead and do the 80e. There are several people who are on here who have done the swap and can help you every step of the way.