Yes, and which proto-Christians? The various so-called Gnostics (more of an umbrella term), the Ebionites, Marcionites, the Johannine community, Pualine teachings (excluding the Pastorals, probably not a bodily resurrection, and with a more platonic view of the heavens), or whatever Jesus, James and Peter actually taught, which is probably lost to history, but would have likely been a form of messainic apocalyptic Judaism.

I found your second sentence very difficult to parse, so I'll ask you to clarify: Who do you think held the view that there wasn't a bodily resurrection? And, what is your basis for saying that they didn't believe in a resurrection?

James Tabor's analysis of Paul's letters is that Paul thought Jesus was transformed into a spiritual being, as the first of a new kind of Adam. As such, there is no point in the body being restored to life. Paul also never mentions the empty tomb or Jesus appearing in a physical manner to anyone as found in the gospels. It's important to read Paul on his own terms, since his writings are dated a decade or two prior to gMark.

Separately, there was also Docetism, which said that Jesus didn't suffer on the cross because Jesus only appeared to have a flesh and blood body. The gospel writers may have been trying to argue against such an interpretation by having Jesus eat fish and Thomas touch his wounds, which would have been ridiculous to Paul given Tabor's interpretation (although Paul was about transformation or exchange of the body for the spiritual).

I don't think you can read 1 Corinthians 15 as merely teaching "transformed into a spiritual being". Paul says 1) that Jesus was raised, using that as proof that there will be a resurrection of everyone else, and 2) that the resurrection body isn't like the pre-resurrection body. It's "spiritual" in the sense that it's fit for heaven.

That does not mean that Paul is teaching "transformed into a spiritual being". "Resurrection" doesn't fit for that. That's "died, and there's an afterlife". But over and over, Paul says "resurrection" - not just that there's life after death, but that there's resurrection.

Tabor's view seems to be forcing Paul's writing into a pre-conceived position, not letting 1 Corinthians 15 speak for itself.

I guess that depends on Paul’s use of the Greek word(s) we use for the English word resurrection. If the Greek literally means “raised up”, does that mean the body was reanimated, or Jesus ascended into the heavens? Paul doesn’t have any post-resurrection narratives of Jesus walking around in his reanimated body.

I can't comment on the Greek (at least, not right now), but Paul over and over talks about a body in this. It's a different body, but it's still a body. That's a huge focus of the discussion.

If Jesus "just" ascended into the heavens (as a spirit), Paul's discussion makes no sense. Paul clearly thought that Jesus had a body after the resurrection, no matter what Greek word for resurrection he was using.

It would be a spiritual body made out of pneuma, like the angels. Spirit meant something a bit different to the ancients. Pneuma was a substance. The supernatural was literally above in space for them. Why would a flesh and blood body ascend into the heavens where the spirits lived? Anyway, Paul had an ancient Jewish/Greek view of the cosmos, not a 21st century one.