Newly built 360 is running weird in 3rd gear

[Shmopar74]

Hey, first post here. I just rebuilt a 1974 360, bored .030 over, 9:1 pistons, edelbrock performer heads and intake with edelbrock 750 on top. The cam is .308 duration on the intake and .316 on the exhaust. Installed in a 1974 w200 power wagon. Im using zinc spark plugs and the original distributor and exhaust manifolds until I can afford all the new fancy stuff. I noticed that in third gear the motor bogs slightly when I hit 3000 rpms and it just loses it's power. In first and second gear I can't notice it bog at all. This is also the first motor I have ever built. Any help or advice you guys could give me would be awesome

 

[Montclaire]

What converter are you running?

 

[beanhead]

Auto trans? What are the converter and rear gears? Tire height? Cam seems kinda big for a truck unless the rest of the drivetrain is well matched..

 

[Don Frelier]

Assuming timing is good.
It's likely that the carb is too lean.
Try larger secondary jets.

 

[Shmopar74]

Manual 4speed with 35 inch mud tires and 4.10 gears. I don't know much about carbs and the secondary jets so I have some reading to do.