[351wStang]

1968 was also the first year for Ford's 302. True 65/66 cars where not made for 351's so they are a tight fit. But I'm putting a 351w in my 66 coupe. The main problem with a 351 going into early mustangs is the exhaust. If you have manual steering and manual brakes you wont have as hard of a time with it. But make sure you have I think its 44" between strut tower braces for the swap. Thats the deminsion the car came with from the factory but over the years sometimes the strut tower braces tend to lean inward.
Yes a 289 can have all the power you want. I knew a guy with a 289/302 combo in a pinto running 9's in the quarter. But he was turning some serious R's. These cars are alot of fun but I would suggest a 289 if its something you think you will want to work on. A 351 can be hard to get to in places in these cars. I beleive that the 351c is almost an impossible swap. I'm pretty sure you have to modify the strut towers for that one.