You say you adjusted the valves on this new longblock. Let me ask you this: did you also retorque the headbolts like is usually recommended?
I had a new longblock 22r installed in my old 1986 4x4. It ran great for 500 miles, at which time I took it back for an oil change, valve adjustment, and head bolts retorqued. It then started to idle rough and smell like fuel sometimes also.
Long, expensive story, but the short version is my mechanic warmed the truck up, removed the valve cover, adjusted the valves, allowed the engine to cool, and then retorqued the head. What he didn't know, and I didn't know either, was that retorqeing the head bolts on these engines will tighten the valve clearance. The engine was missing on one cylinder due to zero clearance on the valves and at least one valve hanging open. A miss means raw, unburned fuel out the exhaust, low power and rough running.
In my case, I checked the compression and got 175,175,150,175 on cylinders 1-4. Didn't think to check the valve clearance because I just paid someone who should have been competent to do that for me. Chased everything else you could think of and finally found a new mechanic who figured it out.
I drove around 1,000 miles with the engine in that condition. The catalytic convertor had to be replaced after being soaked in gas for that long, and the number three cylinder always burned oil after that.
Don't let it go too long before figuring out what's up.