Scott, Forgot to Welcome you aboard!
Also forgot to mention the Holly/Weber is a bit smaller cfm carb, the secondary is smaller. The kits sell for about $80.
Being in the secondary could be several problems. You don't mention what the 250 is in. If it is a truck it could be rear axle ratio. Trucks usually have a high ratio 3.73, 4.10, 4.56, not good for cruising the freeway. It could be the kid is trying to get more out of the 250 than he should or it's due for good tune up. I'm not familiar with the integral head motor. It should have an HEI distributor which is a plus. There have been reports on the boards that the integral heads have a tendency to crack.
Larry
