OldChevyLover,
Yes, there is fender welting between the front fenders and the cab.
Yes, it is better to paint parts before putting them back together. It is also better to "dry fit" the repaired body parts before painting them.
Check out this link for a technique for installing fender welting (I have never used this technique - maybe someone else has and will tell us how well it worked out).
http://www.classictruckshop.com/welting.asp Fender welting can be purchased from most restoration parts suppliers (years ago, I got some at NAPA but it was many year ago).
Good luck,
Tim
