Help altering old Marin MTB to an In-town pavement cruiser? I have an old Marin Bobcat Trail MTB with 26" wheels. I want to make a road bike out of it, and don't want to spend a bunch of money. I just want to be able to go fast and coast for awhile, so I don't have to crunch around on my Talus 29er. 

I'm also ~230lbs and 6'6". I used to blow tires like crazy on that bike. Am I going to be struggling with that same issue with the tiny road tires??

I'd love to post pictures of the transformation. I just need pointers on how to RE-USE what I have on the bike, minus buying new a wheelset.

Thanks all!
There really isn't much required to make a MTB into a formidable city bike.

The obvious thing is to change tires. But I wouldn't actually recommend to go for something skinny just something not knobby. Skinny tires offer very little advantage but absorb a lot less of the bumps encountered in city driving which makes them less comfortable and put the wheels under more stress. Just find some nice (semi-)slick tires and you should be good to go (I just posted my preference in another answer and would feel like over-advertising if I mentioned my personally preferred make and model ;-)).

You may think about adding bar ends which offer an extra position for your hands which is quite comfortable on longer rides.

Most other things are personal preference or at least depend on how you're actually going to use the bike. Depending on your speeds you might want to look into larger chain rings for more top end and, since you're a tall guy, possibly longer crank arms.

Other things to think about: lights (hub dynamo vs battery), racks, mud guards, lock.