Splash guards are available new through several vendors.  My advice is to be sure to get the ones that have the rubber already attached to them.  Then you just bolt them on instead of having to mess with trying to staple the rubber pieces to the steel pieces.  They are not very expensive.  Mustangs Unlimited is a good start.  CJPony parts has them with free shipping, but every time I check pricing, MU is cheaper even after adding the shipping cost.  I guess it depends on where they are shipping it to.
Be sure to check out the annual BASH information.

BGrendal, I have a 66 new 4 row rad. Copper. Used it for a month and switche to alum. PM me and let me know. Also have a starter laying around for a manual car.

The spindles for the 65-66 (maybe other years) are different for I6 and V8, both manual and power steering, in the tie-rod ends.
I'm not sure if the wheel bearings or if the spindel shaft length is different between the I6 and V8 are different.
I suggest you investigate a Mustang parts supplier (on-line) to see the different part numbers for these components.  This will guide you on the differences and what needs to be replaced.
You'll also want to upgrade the rear end to at least an 8", the original I6 rear end (4-lug) will not take kindly to much abuse.