IMO I would pull the rockers and push rods to check them out. If they arent scuffed from the guide plates being there then reinstall the push rods and chuck the self aligning rockers on the shelf. Get yourself some non self aligning rockers to go back on there. Old school small block chevy/4.3s use non self aligning rockers if you dont wanna do the rollers at this time.
You could, however, use the aligning rockers by removing the guide plates IF the heads are drilled deep enough to run the studs down tight without em AND if the rocker studs are long enough to still allow the rocker adjusting nut to do its thing once the valves are lashed.
If the heads arents tapped deep enough then you could cut the push rod "guide" portion of the guide plates off and just use whats left as a spacer between the studs and head. Cheap but a PIA to do. Dont even attempt cutting them with a hacksaw. You'll need a chop saw or air cut off disc to even make a dent in em. BTDT.
Looks to me like the pushrod holes are REAL close to the slots in the heads going by the pics. I would be concearned with them rubbing if you go with 1.6s. Only prob is, to open em up will require pulling the intake to put rags/whatever in the lifter valley to keep out the metal shavings. In a nut shell the slots can be opened up with the heads on the eng IMO but its a PIA to do.
If it was my eng Id check out the push rods like was mentioned. If they are ok then reinstall them. Remove self aligning rockers and install a non self aligning type of 1.5 ratio. Adjust valve lash. Put the eng back togeather and derby the wee outta it. No fuss no muss.