Yeah those 4/4's look sweet but are a fly in the financial ointment of the CBs, for sure. I like having symmetry of at least one pipe on each side, and the chrome. I put some Mac 4/2 slip-ons on my '76 way back when, as the original 4/4's, while perfect from the top view but had what I realize now is probably fixable rust holes at the front lower area - d'oh! Well, that was nearly 30 years ago, the folly of youth and a $100 bike. I chucked them. I got a pair of Macs 4/2's again (pretty cheap at around $220 on clearance) because they look 'OK' and will do until I hit the lottery.
Your bike looks great and you are on the home stretch it seems, really inspiring. I got my '73 top end done yesterday with HD APE studs, all went well and soon will be in the frame.