My boot flung apart going down the interstate on my '57 Plymouth...the boot smacked the floor soo hard I thought something BAD happened. I got a CV boot from an autoparts store that matched the diameter of the original boot.
That lasted a few more months until my car started vibrating badly...the T part of the ball and trunnion shaft busted through the housing! So for about $100 I had a new slip yoke type driveshaft made from my original driveshaft.
Heres a good article on this type of swap:
http://www.earlycuda.org/tech/ujoint.htm
The "NOS" boots aren't worth the effort...they will usually tear apart trying to get them on since they are soo old.
