This is one of the easiest swaps you can do. The K members are the same, just the engine mount brackets are different. You can get new ones through Schumacher for about $175 including shipping. If you decide to use a 904, all the linkage swaps right over. A 727 fits, but it is tight. The pinch weld in the trans tunnel needs to be flattened a little. To run dual exhaust tucked up tight, you will need to modify the trans crossmember since it only has a "cutout" on one side. Its not difficult if you have a welder and a grinder.
There are headers available, but unless you are using a motor with over 300 HP, the $700 cost may not be cost effective. 5.2 and 5.9 Magnum manifolds are the best flowing units besides the 68-71 340 parts. Look for the 1993-95 Full size truck manifolds.