I have a 348 in my 1957 NAPCO, before that I had a 283. The 348 (similar to 409 profile) pretty much fit right in. I only needed to "futz" with the header - steering box clearance. So, on mine the modifications for installing the 283 (side mounts) worked for the 348. However, your year truck, may be more problematic. I have seen a few 409/348s in task force trucks, I just haven't seen any in your era trucks. Seems like it would be difficult.
Steering wise, the 283 and 348 don't seem to be any more effort than the 261 and 235 I had in the truck prior to that.
don
