If you are 'ok' with a manually-tuned low-cost preselector, it might be worthwhile to have a look
at the BCC (Bavarian Contest Club) preselector (design dated from ca. 1998).

There is a brief description including schematics and component data available in English:

http://www.bavarian-contest-club.de/projects/presel/list.htm

On that webpage there is a further link to the full description (PDF) in German.

The design could be simplified to one's specific needs by adapting/eliminating
some of the rotary switches

For the Input and Output transformers (9:1), Mini-Circuits T9-1-X65 parts can be
used, if one doesn't want to wind trifilar on FT-50-43 ferrites.

There had been a discussion back in 2012 at qrpforum.de about the circuitry,
including screenshots of Graphs.
The text there is all in German, however you may just copy-and-paste that into
Google translator. Especially the Posts written by DL4ZAO are quite detailed.
You may also read the Posts by DF5SF, DJ1ZB, DL5CN:

https://www.qrpforum.de/forum/index.php?thread/7840-drehko-alternative-bcc-preselektor/&pageNo=1

73, Klaus, DK3QN