the bar would appear to run directly where the cowl is on the bonneville... and the power steering cap would be covered.

Look at where the mounting points are on the riveira and the bonneville. The Riv/cadillac strut bar would only be able to bolt on one bolt on each side.

i still think that it might be possible...

yes, there may be some modification needed to the cowl cover, and i don't think the brake reservoir is in the way any more than the Rivs

No not the cowl or the resivor. It will not mount correctly at the strut tower points. Look again you will see that the bonneville strut tower only has 2 visible bolts under the hood
the riviera has 3 bolts . The inner bolt and the foward bolt are used the riviera strut tower. The bonneville strut bar uses the outer bolt closer to the fender. The is no inner bolt as you can see in the pictures. Also you have to bend the strut bar as shown here so that it will not interfere with the master cyclinder tank.

are you sure that there is not a 3rd bolt underneath that cowl cover?
i have never seen an upper strut mound that only had 2 bolts, but i also have not looked closely at the 00+ bonnevilles

All diagrams i can find on GMPD, AllData and in the FSM show 3 bolts, one of which would be covered by the cowling.


edit:
what could this be hiding under my cowling?????

Then... It should Work?????

i think there is a good chance... and the $20 from GMPD is not a large gamble if it doesnt

i can get it in 4-5 days from my dealer for $25.83

shall i be the test dumbie?

YES YES YES YES YES!

OH YES PLEASE!!!! This could be a breakthrough for a new mod that we can do to these cars