hmmm ... my 58 came w/ a 6 so I haven't thought about it, just found a shroud to fit when I put a 283 in - my 57 V8 is like like it shows in the assembly manual - the lower core support mount brackets on a V8 frame are riveted on further back than the 6, and the top mounts of it go further back on the inner fenders, and there's a sheet metal piece top and bottom to fill the extra space between the rad and grill - the 58/9 still has the inner fenders shaped to suit that setup, but maybe they switched to using a shroud in 58? they did use shrouds in the 60's trucks
I'll ask a buddy who knows near everything about these ol trucks - but the rad itself is the same as any TF truck - I can take a pic of one for ya and post it later today
Bill