You call your truck a "Step Van", but Step Vans made by Chevrolet didn't come with updraft carburators, they were all down draft.
The Forward Control chassis did have the updraft and they were sold to outside companies like Boyer and Grumman who made bread/milk trucks out of them.
Step Vans are models 3445, 3545 & 3745
Forward Controls are models 3442, 3542, 3742, 6242 & 6642. To the best of my knowledge they all got the 235 Thriftmaster Special engine, so no 261's during the TF years got the updraft carburators.
So, what model is your truck?
Mike B
