If it's all in decent running order, a couple hundred bucks would be my guess if you're lucky...Just don't bank on getting rich.lol People can't giveaway slants these days, let alone sell them. The trans, driveline, and rear end (while not highly sought after with the 7 1/4") might be worth something to the right buyer.
Good luck with everything. I've enjoyed the my slant six for 6 years...But I see where you are coming from when you want to swap it out...They aren't for everybody.