Agree with FrankB, dump most of your position Keep a bit more such that you are still rooting for Oklahoma State.
If you got 1,000 to win 8,000, then risk $6,500 or so on Lakers.
Having said that, don't give away -275 on your whole bet immediately. Grab maybe 2k or so only to make .7 at -275, then put an offer up at -260 and -265 and try to get it filled. DO recognize you don't have that much time. The Laker game will close -6, and that will put pressure on the Series line UP.
Having said that, no doubt some Lakers bettors too them -800 in the series, and may well say ")#$*%*(%# it" and will be looking to lock in a loss and may take your 265.
They can talk talk talk about how good Okl City is AFTER/if they win. Bottom line, it would be one of the greatest upsets in NBA history, and those simply don't happen, partly because the refs won't let it. Ask Sacramento about this.