Thumping under mid throttle.

[HARVEY LIGHT]

Okay, so I've installed the rebuilt 64 Fairlane motor in my 65 Falcon, along with a proper 65 bell housing and a rebulit c4. Along the way I've had a clanking noise which I finally diagnosed to be the torque converter bolts hitting the access plate on the back. After some futzing around I fixed that by cutting some reliefs out where the bolts hit. Now I'm reduced to some nagging items to fix, like how do I hook up a kickdown cable to my Holley-Weber - more on that later. What's got me bugged is a thumping noise under mid throttle. If I back off on the gas it goes away. It doesn't do it in nuetral and I can baby the car up to speed, but I want it to go away. It sounds like something hitting the frame/exhaust but not a clank so I'm leaning towards the frame. Visuals don't enlighten me any. Any ideas out there?
Car info 65 Falcon, c4, 200ci, HW, B&M shifter (prior owner swapped a 170 from a 62 and threw away proper shift linkages and the old style 62 slush-o-matic linkage didn't line up), scarebird discs up front, with maverick wheels to avoid the hybrid 13/14 wheels hitting the calipers, new exhaust from really knowledgeable shop (Built in an extra flange inlet to the pipe in case the donut doesnt seat right. Spent good money but this dang noise is frustrating!

 

[MPGmustang]

two things come to mind...

one, the starter bolts are tight enough to start the engine, and loose enough to move around... try wiggling it... (stupid I know... but I've seen this happen)

two, your oil pump is coming undone, what's your oil pressures? best way to tell is take off the valve cover and start the engine, if oil don't fly everywhere then the pump is loose.

other than that mabye something is unbalanced? u get any strange vibs?

Edit: #3 maybe your mech fuel pump is bad? you could take it off and run the car without it and jsut the gas in the carb... for a few sec's

 

[HARVEY LIGHT]

OK, so #3 is a no since it was a new pump (on a rebuild I try to replace everything I can since I've got it accessible - you know wires, plugs, cap, rotor, yada, yada).
#2 is a possible because when it warms up the oil idiot light comes on. I had thought it was because the idle speed was low and I just reset it to be 150 rpm higher. I get a chance later this week to warm it up good and see if the pressure drops.
#1 I'll look at soonest because it takes the least disassembly to correct if we're right.

Thanks for the tips. Harv