Looking for a 1972 455 HO engine

I've officially gone over the edge...It all started about a month ago when I finally caved into my muscle car craving and bought a 1972 Lemans Sport convertible.  After much hand wringing, I chose this car since I had owned a 1972 4-door Lemans during high school, college and the first year or two of post college life.  The car I bought is in great shape having been completely redone frame-on, but it is in need of a heart transplant as it still has the numbers matching 350-2bbl engine, 350TH transmission and non-posi rearend.

My plan is to install a 455 engine with working ram air and install a locking differential in the existing rear housing.  Based on my research since going crazy, and the fact I won't be going to the track, I plan to keep the 350TH transmission with the addition of a shift kit.

Although the car is a "clone" GTO, I would like the 455 to be year correct and would prefer the HO version since....well since it is the HO version.  I have a lifelong friend that is an engine builder, so I am looking for project engine as opposed to one that has already been built.

I have been impressed with the level of knowledge on this Forum, and I look forward to any help the members of this forum can provide in finding an engine so that I can next have you all hold my hand through the selection of internals and succeeding phases.

Best Regards.