Glen,
I've seen the Poway clasts on the SW side of Santa Cruz Island...I forget is that is the Jolla Vieja or Canada Formation there. If I were you, I'd look at the Abbott and Smith paper (1978) on your link, or a later one by them, and see if one of them is still doing research....I heard Abbott (sp) give a talk at UCSB in late 80s or early 90s, and I think he has a later paper on this. Doing this would ensure that you are not repeating what has been done, and you could find out whether anyone would be interested in looking at rocks you might collect, and to ensure that you collect them in some way that would work for clast comparisons etc (there may be some scientific way of sampling; I don't know. If no one is going to analyse the rocks you look at, might as well look at them in the field and leave them there. I suppose you could look at the papers and analyse them youself (mainly, what type of rocks are the clasts, and where might they have come from...see the papers).
Chris