I'd also buy a pair of SDP40Fs, in the original scheme, as they'd be perfect for my 1974 Empire Builder and North Coast Hiawatha. They'd probably sell better than either the SDP40 or SDP45, and with a few minor modifications, could be sold in quite a few freight schemes.
Personally, even though I model the early BN, I'd rather have them than the SDP40s.
On the other hand, we might have better luck lobbying Athearn for the SDP40F, as they might be able to reuse some parts of their FP45. There was only a one foot difference in truck centers, and the overall length was the same as the ATSF FPs. The "Contemporary Diesel Spotters Guide" notes that the MILW FPs were shorter overall than the ATSF, which is a little odd, as they apparently have the same wheelbase.
