You're not doing yourself any favors by assuming the advice Bowtie Overdrives will provide is worthless because you can't check line pressure. First, checking pressure only requires a 300 psi gauge and a hose with a 1/8 NPT male fitting. Not hard to get a hold of. Second, it is imperative that this system is properly installed and adjusted as the life of the transmission desperately depends on it. As much as you're trying to avoid it, you need to be a bit more 'scientific' in your approach.
Imagine someone building an engine and they say that it won't rotate with the main and rod caps torqued. They don't want to measure anything because they don't have access to mics so they just want advice on how to get it to turn. Same idea here.
Assuming the transmission is currently healthy, it can handle a decent engine. If you do not want to go the pressure gauge route, there's one other way that you can dial in the adjustment but it would be easier with a couple people. You can remove the transmission pan to get a visual on the TV valve plunger. Then you can make adjustments ensuring that the plunger position matches throttle position.
Take a look at this well written article for more insight:
http://www.tvmadeez.com/article/