Yes, a 429/460 will fit in a 70 Cougar. With or without cutting shock towers. If you are talking about a BOSS 429---now that is a different story.
I have cut the shock towers on my car to make life easier with changing plugs and installing header bolts.
I have moved my radiator forward to allow enough room to put my electric fan onthe inside as a puller. A pusher fan is only 80% as efficiant as a puller.
You can use the balancer and water pump from a 69 Thunderbird to allow more room then using a the standard truck or lincoln componants. THe T-Bird's water pump is shorter and the belts ride right on the balncer.
I have used the Crite's Restoration swap mount and header kit to install the 460 into my car. One of the problems I have found with using their kit is that the headers are very big---about too big for a mild motor. I also couldn't make a complete left turn sinc ethe pitman arm did hit one of the header tubes. I then went to the FPA shorty headers which also had a smaller diameter at 1 3/4" primary tubebs versus the Crite's 2" tubes. I drive my car a lot and I live in Florida so it heat becomes a problem. With the big headers there was a lot more underhood heat. The smaller headers have less surface area and thus radiate less heat.
When selecting a header, it is important to take into consideration a tube size that would best compliment the engine's combination and desired use. Say if you have an engine that is going to put out a lot of power you would opt for a biiger tube diameter. And like wise with a mild motor. But, if you had a higher HP motor and 99% of the time drove the car like a normal car, it'd be best to select the smaller header.
I drive my car on a daily basis putting well over 10,000 miles a year, so I had decided to go with the smaller header which had not caused turning restrictions, didn't radiate as much heat, was quieter and servicability was easier. I would have just gone with exhaust manifolds, but the next engine's combination would have required something better then the log type manifolds. If I had a full effort type of motor, I would have stayed with the long tubes, but then the drivability of the motor would have been very poor making it only a racecar.
There are many options and directions to take when making major changes to a vehicle and you will have the best performance from a combination if you choose componants that compliment each other.
Hopefully I can offer some advice to help you get the desired performance, just let me know if you have any specific questions.
thanks,
Mark Piechowski
70 XR-7 460 AOD
69 SS 351c 2v AOD
70 XR-7 convertible 351c 4v FMX
69 Sunroof Eliminator 351w 4v FMX