Read my posts here for online suction side screen: R4 Compressor Siezed.....

Go to a GM parts counter (Pontiac for sure; others most likely as well) and for ~ $2 or $3 they should hook you up.

There are suction side filters, but they're larger and require some hose rebuilding skills.

Here's a high side filter (if you like high side filters) that gets good reviews: http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=inlinefilters

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)