For one, you'd have to order a GT40/Cobra style intake, larger injectors, MAF meter, a special oilpan, pickup, headers.

That was including a rebuilt H.O motor, the intakes, injectors, computer and T-5 tranny that I haven't installed (still using the AOD). I spent a whopping $900 on my H.O 5.0 conversion. While it's not horribly difficult to use a 351W instead of a 302 H.O, there are alot more obstacles and expensive parts to buy that you wouldn't have to worry about with the 302 swap. For one, it's difficult enough just to wire up a V8 harness in a Four cylinder car. I'm working on the 351W EFI swap right now for my Cougar.

Unless you're looking to get more than 380rwhp, It's not worth it to do the 351W swap. Your 4 Cyl drive shaft will bolt in to a V8 T5. You will have to replace your fuel pump with a larger one, and the fuel lines will need to be changed to a 88 V8 Tbird. There are differences between each year of TBird, as well as being different from a Mustang. I have an extra one, if you're intrested. Ford had a TBird 'Sport' model in '88 that had a V8 tach that will fit your instrument cluster. Your tach will have to be converted to read 8 cyls, I don't know who does this now. If the TurboCoupe has a hydraulic clutch linkage, you will need to swap it out for a Mustang pedal assembly. You will have to extend the pipes after the mufflers because the chassis is longer on a TBird. Mustang headers will work, as well as a Mustang H pipe. You already have a good rear axle, so no problems there. A Mustang double hump trans mount is a bolt in. Also, there are no better aftermarket mounts available. They are silcone filled and not the best for locating the motor. Most Mustang parts will fit, You need to determine which K member you have, If I has a 'perch' that the motor mount sits on, you will need 88 V8 TBird motor mounts at about $80.00 each. I have a 5.0/331 in my 86 TurboCoupe, which is basically the same car as an 88.

88 turbo thunderbird