Fatman lowerd the steer-arm holes to eliminate bumpsteer issues on Camaros and Novas. This worsens bumpsteer on Chevelles.
To use the Fatman spindles, I'd recommend also buying ATS's billet steer arms (they did the same thing on their spindles, but were smart enough to know they'd have to do something to fix it, which is what their billet steer arms are meant for) Some grinding will be necessary to get these arms to fit the fatman spindle though.
The SC&C tall balljoint packages are a much better option.
SC&C's adjustable upper A-arms are also much cheaper than GW's and offer the benefit of adjustability.