90 Ranger speedo & tach problems

Two problems with my 90 Ranger S-Cab w/2.9-A4LD auto, no cruise. My speedo is reading "faster" than actual mph, and buries itself at 85 after hitting 65 mph on dial. Needle movement is smooth, not jerky. I've just done a tranny swap- like for like- and both A4LD's had 17 tooth cable drive gears, and speedo worked fine before the trans swap (truck sat for two years w/wasted A4LD tho). Any one have any ideas as to a fix?

Problem #2- my factory tach will intermnittantly read 500-1000 rpm higher than "normal" (idle norm at 750/800 will read 12-1400 rpm, cruise in OD at about 65-70 mph normally about 2100 rpm will read over 4000). I haven't found in my schematics what Ford is using as a tach driver. Is it tied into the speed sensor/speedo drive head on my trans tailshaft? Do I have a bad ground somewhere?? Help, please???