M151A2 sluggish in 3rd and 4th gear

[jamboly]

I am working on an M151A2 that I got last October that I want to get "road worthy". I replaced the electronic ignition module with one from a used distributor that came with the mutt. I put a new carburator on it. (acceleration pump is not working right, but I don't suspect it is leading to my issue) Timing looks to be okay. No white smoke in exhaust. Seems to idle okay. I do have a fairly bad oil leak, but clutch doesn't seem to be slipping. However, when I take it out on the road and get to 3rd and 4th gear, it just seem sluggish. It takes awhile to get it up to 50mph and I am lucky to get it to 55. It may just be that I am not used to driving a vehicle with this size engine. I know specs say max speed in 55mph, I was just expecting it not to struggle to get there. It is just me, or do I have a problem?