FE is listed at 625lbs and 429-460 at 720lbs....Lets say closer to 100lbs than 20?

My brother blew up his 69 Mach1 428CJ back in the mid 70s and swapped in a 429 thunderjet...He modified the stock 428 mounts to fit the 429 block by simply drilling a couple extra holes to match the 429 blocks bolt pattern...
He said the 429 was actually easier to change the plugs on as it is a hair narrower than an FE motor..The 429 is a tad longer though so fan clearance at the rad is very tight...A 69 Tbird waterpump can help out as it is a bit shorter..

 

I started this untill I actually set the motor into the car, it looked like a beached whale setting in it on the mounts.

Went back to the small block since I had a couple of them setting in the shop.
I had already added after market reinforcement to the structure motor mount shock towers.

Can't Imagine putting one of the beast in a car with the stock small block shock towers. A close look at many of the older Mustangs and Cougars they develope cracks in the shock towers with the small blocks alone.

 

any pics?

 

https://mustangforums.com/forum/memb...rs-cougar.html

 

No such thing as a "small block shock tower". In 67, all 200, 289, 390 and 428 Mustangs, had identical shock towers, and also in 68, except in "68 1/2" Ford introduced the 428CJ, which had reinforced towers. In 69 more cars, including the BOSS 302 and 390 had the reinforcements, and at some point, they were added to convertibles, either at or near the 70 change.

In my experience, cracks in the towers had a lot more to do with aftermarket positive offset wheels than the size or power of the engine. Every 67-70 289/302 Mustang I have seen with cracks either had "mags" or used to.

Either way, adding the reinforcements is dead easy.