Could be either a 289 or a 302 with that block. Depends on which crank and rods are in it. "8B6" tells me the block was cast on Feb. 6, 1968. As Frank pointed out, your front mounted dipstick ain't gonna work with a rear sump pan. A peek inside the crankcase when you swap pans will tell you exactly what you've got and if it's got forged pistons. And do not toss any of those parts off the motor, they're all worth cash on ebay. That aluminum bracket on the front of the passenger side head brings about $15-20. The accessory brackets and pulleys go for about $40 or more.