A couple of things. The 502 is in fact a direct drop in for the 454. See my sig. As far as bolts or changes, the only things that I had were the bolts on the front of the heads were one size larger, which is a non-issue. All the brackets still bolted on. I did have to barely open up the bolt hole on the alternator, but for 5 minutes with a drill, this is also a non-issue. The engine mount on one side required some tweaking with a sawsall. Because my coach is front wheel drive, I had to tweak the 10 qt oil pan to fit over the differential. This of course is not an issue for you.
For the trans, I recently converted to the 4L85e. Currently using a EZ TCU, which can be purchased from Summit - Current price is $614.97. It is a very good controller, and very simple to program. I like the way it responds, and even though it has the option of manual push button shifting, I never use it. Once in a while, I do switch to performance mode, which changes the downshift points, and increases pump pressure.
As far as fuel injection, mine is based on a GM ECM, which could also control the trans, but in my case, when I first installed the trans, they forgot to install the rear speed sensor reluctor ring. I blamed the weird shifting on the ECM, an bought the EZ TCU. I've since got the trans straightened out, but have not bothered to go back to the GM ECM for trans control. I'll switch it back someday. If you can get around computers pretty well, you could piece together the fuel injection. There is a lot of help on learning to burn chips. I could send you my program, which would give you a good starting point. Mine is set up for multiport, but the ECM only cares about total fuel flow, not how many injectors are hooked up to it. You would have to play with it some, as a duel plane will act different than the Edelbrock.
For numbers, the engine comes in around 420 to 440 HP, based on acceleration tests, which was consistent with desk top dyno calculations. The coach weighs in at 13,580 lbs. I get just over 9 mpg, cruising 72 to 75+ mph.
Biggest question I would be asking is if your coach has any delamination, or has had any signs of leaks that were neglected. Fleetwood products from that era where known for delamination. If you have areas, specifically look below the windows, where the siding is soft and sagging away, then there is no point replacing the engine.
