Weird Transmission problem?
 

Hey everyone I bought a 87 ram 50 with the 360v8 and 727 automatic transmission swap about 2 days ago.The issue I’m having here is the truck shifts through all 3 gears just fine but it tops out at 40 miles per hour with super high rpm’s,Where should i start looking to fix this problem?
(1st -2nd gear 0-20mph 2nd-3rd gear 20-40mph)

Check to make sure the TV cable from the throttle body to the transmission is hooked up and adjusted correctly

Yeah I checked that earlier today and from some videos I’ve seen it looks to be adjusted properly,I can send some pictures later.I think it may be the wrong kickdown cable since the guy I got it from put on an aftermarket carburetor,I’m not too sure though since this is my first carbureted truck.I’m used to working on motorcycles

Check the torque converter stall. Place in drive with foot on the brake. Accelerator on the throttle and check your RPMs. They shouldn't go over say 2800 rpms. If it does your converter has failed and isn't locking up.

Sounds good..... Also, Pull the dipstick and see if the fluid is still pink or is it darkening and smells burnt?