Atmadeep's Mk4 build - Need help!!

[edwardb]

Your planned Roush SBF 427 is based on a 351 block. Those 16434 427 Headers are for an actual big block. No go. Assuming Roush is using standard height heads (only they could answer this question) then you need to use headers for a 351.

For the 2015+ Mustang IRS diff, you would typically buy the complete assembly. There’s no reason to buy the Torsen or any other parts separately unless you’re looking for a non-standard combination. Even then, you likely would want a pro to do the work. There are special tools and various size shims needed to set up the internals of a diff. Factory Five offers the complete diff which you can add during your kit purchase. Search M-4001-88355 for example. Or you can buy them yourself. They’re sold by Ford Performance (aka Ford Racing) through multiple channels. Forte, Summit, American Muscle, CJ Pony Parts, Don Woods, etc. They come in a number of ratios (3.15, 3.31, 3.55, 3.73) and iron or aluminum case. I would recommend staying away from the 3.15 ratio. The internals of that one are not compatible with any of the others. If you do choose the 3.73, those only come in the Torsen version. At least in stock form. You’ll also need the IRS knuckle/hubs, also available from Factory Five or separately. Search for part number M-5970-M.

Not quite understanding your concern about the axles. IMO the ones from Factory Five are fine for your build. They’re quality pieces. Similar builds as you're planning are using the provided axles. If you were still looking at that 700+ HP option and real sticky tires, plus planning hard launches, maybe you would want to look at something else. But for what you’re planning, I’d stick with what they provide.

There’s no way to give a good answer on paint costs. There are so many variables, and the prices in my observation seem to vary widely by region. Some variables include how much you plan to have done (e.g. only paint, or also all body fitting, gapping, etc.), what color (can make a big difference), what brand paint is used, stripes/no stripes, etc. It could be as low as 5-6K (unlikely if you really want show quality) or well over 10K. Or somewhere in between. FWIW, the job is somewhere in the 150 hour range plus materials. So no surprise it's not cheap. Highly recommend that you search and only use a shop that has done these before. Not just the fiberglass aspect, but know they’re way around these specific bodies and builds.

The build school and the order process should answer a lot of your questions. When you actually place your order, Factory Five will walk you though your planned configuration and tell you what works and what doesn’t. They will make sure you have the right driveshaft, brakes, etc. to match your build plan.