I'm not a professional, and some of this could be wrong. But I did learn a little when I installed roller rockers on my Lt1.
The OEM stud size is 3/8" and you need self aligning rockers or you will need to use guide plates. The rockers must be a "narrow body" design to work with center bolt valve covers and OEM valve covers need the baffles removed for the extra clearance needed.
Proform makes an aluminum roller rocker that seems to be quite popular with the centerbolt guys and runs under $180 per set from both summit and jegs, Or at least they where a couple of years ago when I was looking for mine.
I purchased my 1.6 stainless steel roller rockers off ebay for $119 shipped to my door. They are cheapo knock off's, But they have worked well for me over the years and the quality was better then I expected. I originally put them on a Barnes & Reese short block with ported Lt1 heads, But after approx 7K miles one of the wrist pins broke and destroyed the block and heads. Now I have them installed on my otherwise stock 94 Lt1, And have put close to 10K miles on them.
But any SBC roller rocker with a 3/8" stud and narrow body design will work with centerbolt valve covers. Oh and don't forget to change your springs as well, The LT4 springs work well.