Max;

...it seems to me that an owners manual (or even just the little piece of paper which lists which fuses protect which functions) would have been been enough for this issue, but a full shop manual is always advisable to have for a 50 year old vehicle! Factory Green manuals are the best and most complete, but Intereurope and Haynes are very good alternates. See: http://www.sw-em.com/library.htm

Fuses should be installed with a dab of ACZP for long-term reliable connections which are not susceptible to corrosion caused intermittency. See: http://www.sw-em.com/anti_corrosive_paste.htm

25A shorty fuses are somewhat rare, but there are sources for them. See: http://www.sw-em.com/swemkits.htm

If Mechanic determines that the homemade 25A fuse is a little too squirrely, you can have him remove the homemade, and have him bridge a modern a modern fuseholder with 25A fuse across the terminals which connect to the 25A fuse, while you procure the correct 7X17mm shorty.

I'll see if I can post or link a pic of this fix...

Cheers