I am looking at a Cafe racer from 1989 that has 525īs in it.
Are they 420īs with a blower or do they have different pistons, cams ect. ?

Cigaretteman

With a cig of that age, it could be a Hawk or Merc 525SCs. They both have similar specs.
454 cid block and heads similar to 420
7.5:1 CR
Weiand 177 blower
Hollet 1050 (Merc) or 850 (Hawk)
rectangular port iron heads, roller rockers
525 hp
Velvet drive, TRS (usually)
Both very good motors in my opinion.
Gary

Do a search for "525SC" you'll find all the onfo you're lookin for.
The Cig probably has Hawk engines.