My '67 big block would top out at around 145 but it was a mild build with 3.36 gears. It might take some research but I doubt if the L88 racers ran much over 160-165 at LeMans. Aerodynamics is a limited factor on these cars. It would take a bunch of horsepower to push one of these bricks to 200 plus some aero aids to keep it stable. Normally you figure a 20% horsepower loss through the driveline and this guy is saying over 45%. Tell him to get his foot off of the brake and it will go faster.
For comparison take a look at the current issue of Hot Rod Magazine. They have a feature on Chuck Mallet's slime green 435 inch daily driver with Vortec Blower. It will run in the 10s in the quarter with a 3.4 or so 0-60 and top out at 220.
I think that Gale Banks holds the record for fastest stock bodied top speed with a slicked up Firebird and a whole bunch of twin turbo horsepower. He has topped 300 at Bonneville but it takes a lot of power and a very slick body plus years of refinement and trying. A stock '67 body just isn't going to do it.
Tom