it depends on your budget, and how modified you want to go. There are several companies that make suspension kits including
http://www.totalcontrolproducts.com and flaming river. TCP has some really cool stuff, but they are rather pricey. Flaming River also has a MustangII rack and pinion kit, but once again it aint cheap.
You can fit a 351w into a 66 without removing the towers too. I know NPD has a line of 351w swap products, along with 5.0 swap stuff. From what I understand the swap itself is pretty straight forward, but you'll need several new parts, ie headers, possibly a hood (since the 351 is a bit taller) oil pan etc. Depending on what tranny you are going to use there are other things that might need replacing too.
Are you looking to go carbed or EFI? Stick or auto? Whats currently in the car now?
Hope this helps
J
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'66 Mustang Coupe- AKA "Lenore" *on disability for a (long) bit*
'93 GT Mostly stock AKA "Fawkes"
Rice Haters Club Member #239
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