Lets play guess the noise

[1985K10]

My 85K10 started making a strange noise about a month ago. When I'm cruising and have enough throttle to maintain my speed, and any speed, I get a kind of rattling noise, it goes away when I let off the throttle, or when I accelerate. But when I try to stay at one speed it does it. Its definitly coming from the engine or the tranny. Sounds like its between the back of the motor and the front of the tranny, which makes me think its the distributor, or the torque converter.

Extra info-Theres also a lifter that ticks untill the engine reaches like 160 deg, my engine is a 350(87 or up cuz the centerbolt valve covers),w/new Eddy carb, stock intake, HEI, the tranny is a 700R4 out of a 84K10(and the T/C), and was originally from a 84 Blazer. My lockup is working Just fine, well, it locks up in second gear, O/D works fine, the noise occurs in and out of O/D. Everything works fine, the truck drives fine, tranny feels smooth.

It almost sounds like its a couple metal plates clanking together. So my guess is the clutch in the lockup T/C.