i'm driving an 85 riviera and the stock 307 is about to quit on me. i want to replace it with a 350. i know they came with an optional 350 diesel from the factory but i want wondering if there should be any problem stuffing a 350 under the hood

If I'm not mistaking there is no fysical difference between the 307 and the 350 so you won't have a problem

I think you can put a 403 in place of the 307, and REALLY make it run. They are all pretty much interchangable.

Bob,
The 307 is an Oldsmobile engine. If you want to go with a 350 with the least amount of hassles, it will have to be an Olds 350. Any others (Buick, Chevy etc) will require completely different accessory brackets, exhaust etc.
I personally would not count out the 307. They usually last forever if the oil is changed pretty regularly. Find a good local machine shop to rebuild it, add a slightly bigger cam from Mondello performance, and you will be surprised at how good it can run.
Hope this helps,

The 403 I refered to was also an Olds engine.