I'd like to try and clear up some things here...
The 1975 Sidewalk Surfin' redux by Dean did not 'intentionally" leave Jan's voice off. Skateboards were exploding, particularly in California - and surf music was in the middle of a major comeback. Dean felt it was the perfect time to re-issue SS with updated lyrics featuring skateboarding slang from the mid 70s instead of mid sixties. United Artists agreed to release a single - but then refused national promotion money. Despite all this the song was still number one in various California radio markets. In 1978 Jan was preparing his disco remake of SSUSA... he needed a falsetto singer and called Dean for Brian Wilson's phone number. Dean asked why... when Jan explained what he was doing Dean volunteered to sing the part himself.
The 1977 Remakes...
There are three sets of masters as far as I can recall from the mists of time. The KTEL masters were among the early recordings. In late 77/early 78 Dean prepared a new set of recordings for a DMC soundtrack LP to be distributed by RSO. The LP included DMC, Sidewalk Surfin, Little Deuce Coupe, Little Old Lady, Surf City, Teenager in Love, One Summer Night, Get A Job, I Only Have Eyes for You, Barbara Ann (an uptempo version with a track like the 1962 recording but heavily overdubbed - and a "Thank you Carl" nod to Carl Wilson at the end), Pipeline and Wipeout. Many of the tracks were actually in the body of the film. The J&D remakes were actually great sounding, with the addition of brass and instrumental sweetening which made them sound big and bold, like the original recordings. Apparently, at one point, the filmmakers were considering using these new remakes in the film instead of the Liberty masters. The only time I saw this collection surface was on a vinyl LP from Australia. I've never seen these tracks surface on CD comps. There are versions of the 50s remakes from the film on CD - but not the final, lush mixes included on this vinyl release. Teenager In Love and I Only Have Eyes for You are particularly powerful. Apparently the RSO release fell apart over a disagreement over who would retain Japanese rights... a lucrative territory. UA's entire controibution was a re-issue of the Anthology album later that year with a tiny little yellow sticker reminding buyers of the Deadman's Curve film.
The third set of masters was a new Deadman's Curve soundtrack scheduled for release on Mike Nesmith's Pacific Arts label. These were newly recorded tracks (in 1978) featuring Dean with members of Papa Doo Run Run and Mike Love with members of Celebration. I think Ron Altbach was involved in production... all of these tracks were newly recorded... the "phone" version of DMC... the legendary bluegrass version of Jennie Lee which featured Jan Berry... etc. This also remained unreleased although many of the tracks ended up remixed and augmented on Silver Summer. And the original 1978 mixdown has popped up on various CD comps. And that's what I remember from those heady days in the fall of 1978... I remember Mike Love and Bruce Johnston talking about producing a Jan Berry solo album that fall as well... so us fans figured we were about to be hit with all sorts of new stuff. And then none of it ever came out...