A couple of suggestions ...

Dallas 80C390
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http://dbserv.maxim-ic.com/quick_vie...qv_pk=2956

This device has two serial ports and two full CAN 2.0B controllers.


Triscend E5
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Similar CPU to the Dallas device. You can build UARTs that operate even faster than 250kHz. The on-chip DMA controllers handle moving data to and from memory, either internal or external.

No internal CAN controller but here is a reference design that may be of interest.
RFD-02: E5+CAN (135K, .Zip file, Jan. 2001)
http://www.triscend.com/products/...10_i2p.zip