Late model Mustang 5.0L shorty headers work.
Motor plates work fine, if your handy with a welder you can adapt the factory 302 mounts easily with a home made adapter to the front crossmember but it will sit a little high.
Better be handy with the sheetmetal if you want a C6 in there, you will have to cut the entire trans hump out to make it fit. C4's are a no brainer and fit under the stock hump.
A stock Bronco 302 oil pan is required to make the engine fit properly, you can cut a stock rear sump and turn it around to make it a rear sump if your tight on cash but the factory sump material is thin...a stock Milodon replacement pan is much thicker and easier to modify. You will need to fabricate a longer pickup of course but you can use a stock pickup with an extension tube and rear mains stud hanger. Cutting and welding a new stock replacement pan from Milodon is a lot less hassle than trying an old factory 302 pan, the oil contamination is impossible to get completely out of the metal and it wrecks the weld.
To be honest the kits are worth the cash if you count your labor time as money, but anything is possible with ingenuity. BTW the stock rear ends won't handle drag racing. The only thing close enough to fit is the early 70's 302 Maverick 8" axle housings and they are still too wide...but they come with spring perches and are beefy enough for about 500HP rebuilt with a good set of gears and new bearings. New axle shafts will be required anyway so get some custom Strange ones made to fit the housing when its shortened.
Don't shortchange yourself on the rear axle and driveshaft by trying to go cheap here, the short wheelbase of the truck loads it heavily at launch and the stock stuff is junk.