I'm just saying, a 4.6 swap is not for someone on a tight budget. Yes, there have been some really nice projects using modular engines, but I guarantee that you won't find a single person, who has completed such a project, claim it had a relatively (to, say, a carbureted SMF setup) low cost, even if a free donor engine was provided. Also, I've heard from others' experiences (haven't attempted to put one in myself, that's why I haven't given exact instruction) there's hassle elsewhere than simply wrt fitment. I bet the price just to get one to work in the car will outweigh the cost of finding a run-of-the-mill 302, rebuilding what is necessary, and doing exactly what I mentioned above.
As we all know, it's very easy to exceed cost expectations when working on these cars, especially if one's attempting to something rather unusual such as adapt a TC 4.6 into a '69. I just don't want him to start and project, get in way over his head, and then be stuck. I'm not purposely withholding information, I'm just offering whatever educated advice I can.
BTW, I take it the Towncar will be rendered useless without the drivetrain. If the car is decent and running, why don't you simply sell the complete car, and use that money (should be more than enough) to buy a nice small-block and matching trans?