I am loo.king to buy a front driveshaft for a conversion project.
I have a 5 speed transmission out of a 1993 190e 2.6 that I want to put into a 1993 300ce.

Last year I did a conversation auto to manual in 1989 300CE and I used the driveshaft from a 1988 300E. You are not going to find a driveshaft from a CE with a manual transmission according to the Mercedes bible Mercedes only imported sedans with manual transmission

If you take your existing drive shaft to a drive shaft shop, shortening it or lengthening it and rebalancing it shouldn't cost you more than $200-$300. That way you'll have an exact fit and good balance, and, depending on the shop, maybe a fresh coat of paint.

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I never go far without a little Big Star

1994 E500 199/Gray 82k
84 300D (Salty) Orient Red/Palomino 141k
88 300CE (Ersatzhammer) 904/Java 163k -- Turbo Technics twin turbo kit, AMG Gen I body kit, Sportline steering box and steering wheel, Sportline/Eibach /Bilstein Sport/500E suspension, Quaife LSD in 210 mm diff case, Silver Arrow brakes.
88 300CE Brabus 3.6 199 on Black 44k

Did you use a 1988 300e manual front shaft or a 1988 300e automatic front shaft?

I used the manual DS but the 88 has the smaller differential and I think yours have the bigger differential