NO , NO , NO Revtech!
Probably about the same money to but a complete S&S motor , or have a Sidewinder kit put in your cases.
As for retitling , depends on your states DMV laws. The frame has the VIN , the motor has a partial VIN. Aftermarket motors come with a Manufacturer's Statement of Origin. Ya can either file paperwork and get a reconstructed title , or simply swap motors , carry a copy of the MSO and receipt to show to , and tell any cop who actually knows the motor ain't original , that ya intend to replace the original motor if ya ever sell the bike.
The motor in my Panhead is an STD cased , S&S filled 93" stroker. I carry a copy of the MSO with me. The original motor is sitting on a stand in my living room. Cracked cases and all.
It might be legal for you to stamp your motor numbers in the new motor cases as long as you DO NOT alter or remove any manufacturer stamped numbers.
There's no attempt to commit fraud and ya can prove legal ownership of everything.