I have one in my bird. IMI Hi-Torque. Turns my 463 CI 10.5/1CR over in 100F+ temps after driving four hours and it's so hot my wife and I are getting heat exhaustion.
The basic motor itself is the same on these for most applications and it's only the adapter block that is type specific. I think, don't know, that the same one fits Chebby and Pontiac. One has to index the motor on the block to rotate it as far away from the exhaust as possible. I can't see why yours would get heat drag unless it's resting right against the header pipe. Or is it the stock starter you have the heat soak in? My 69 GTO had a real heat problem, put a new starter in and same thing, put a mini starter in and presto! Worked great.
One thing I would recommend is using a Ford style starter relay, that re-routes the Purple 'start' wire away from the starter and heat. The 'start' wire from the ignition switch goes to the remotely mounted relay and the only wire that goes to the starter is the cable. The cable is only electrically charged when the key is in the start position. A jumper is included with the starter to hook up this way. See the beautiful drawing I had commissioned at Great sacrifice and expense. I have the charge wire going to mune, it's a great place to attach accessories as well. I've hooked up my remote start switch to it a few times as well while setting up the.engine. I have mine Mounted on the inner fender right near the battery, but if you are worried about originality they can be hidden.
One problem I did have was the aluminium block came loose from the starter, had to roll down a hill to get it going to get home. Some lock tight on the bolt threads have solved that.