I have a bone stock 86 305 TPI. its a factory roller cam engine .I would like to use some roller tip rockers ,I would like to know if ,,,first, will they fit under my factory valve covers?? second are there any gains to be had if I use 1.6 rto?? im probably going to use comp cams parts.suggestions?? it has a stock camshaft also. im using a set of stock "416" heads.with flat top pistons

Depending upon exactly what type you're talking about, they'll probably fit.

Going to 1.6:1 will likely not result in a quantifiable improvement in power, and will likely overwhelm the stock valve springs.

I suggest going full roller 1.5 rockers. Stay clear of those 'roller tipped' rockers. The full rollers have much less resistance where it really counts. Wait to get 1.6 rockers until the heads are replaced with valvetrain that can safely handle it.