I tow a 2001 Jeep Wrangler with a 5-speed manual behind my Chev Duramax dually which usually has a large Lance camper in the bed. The picture below was taken in 2012 (the 2006 truck has since been replaced with a 2015). I can't even tell the Jeep is back there at reasonable Interstate speeds (generally under 68-70 MPH). The Wrangler can be towed all day at any speed. Just put the trans in 5th gear, the transfer case in neutral and unlock the steering column by placing the key in the unlock position between the lock and accessory positions. I also ran a trailer harness from the front of the Jeep to a second set of taillights I installed in the Jeep taillight housings and a hot 12V wire from the truck to keep the Jeep battery charged.
That said, I think a '73-'91 Suburban might be somewhat "weak' depending on its drivetrain and if it's a 1/2 or 3/4 ton. As you know, your towed vehicle with an automatic will require different treatment. If I recall correctly, some vehicles with automatics can be flat towed with the driveshaft connected. However, this usually requires stopping occasionally to run the engine for a while to circulate the trans fluid. As mentioned in posts above, you'll need to discuss that with a Ford expert.
If you tow any distance you should/need to buy a quality tow bar and an auxiliary brake for the towed vehicle. I use these:
https://www.campingworld.com/stowmas...ets%2Ftow-bars
https://www.ebay.com/itm/Brake-Buddy...75.c100623.m-1