Not sure about a 4v ,but a 2 v fits with no problem .I dont know how much wider a 4v is but at the most you may have to notch the towers a bit . I saw a 2v transplant and it looked right at home .
shouldnt have to modify the shock towers as the 429 fits nicely in those cars. a 98 cobra motor should go in quite nicely, and you should have a lot of fun with the end result.