My brother and myself switched from wieand TR's to M1 TR's and seen no noticable difference other then increased hood clearance, no performance change noticable, mine was on a fairly mild 440 in a 63 dodge running 11.20's-11.30's, his was on a 383 duster running 10.70's-10.80's

on a side note, I did switch from 2 500 cfm carter comp series too 2 750 cfm carter comp series on the same 63 dodge and picked up a solid tenth, maybe 1.5 mph, most of the gain came in the 60'! then I switched too 2 750 cfm ebrocks and they ran the same as the 750 carters...as noted earlier a switch to 2 750 race prepped dp holleys made no noticable et gain over the carters on an indy headed 440

a run down on the car, 63 dodge, 3540lbs w/driver
4.56 dana on leaf springs, 13x31" rear tire, 10" street/strip type convertor, .060 440 , stock crank&rods, KB pistons, home ported heads w/ 2.14/1.81 valves, 10.5:1 comp ratio, cam was an old lunati .540/.563 lift and 261/271 duration @ .050, TR 2 750's, car ran 11.20's - 11.30's @ 119 with 1.57-1.58 60' , fun car, wish I had it back