Thsi sub-page has your '74 scematic; you just did not go down far enough in the layers:
http://www.mymopar.com/index.php?pid=28
'A' on the fuse may be something like 'AGC' which is a style of fuse. What you really want to know the the '5A' or '15A', which stands for 5 amps or 15 amps or however many amps the fuse is rated for.
If you have 2 fues only with power try the folowing 2 things: If the horn works, and if the brake lights work, then those 2 fuses are likely for those circuits (plus several others that hang off of the same fuse as the brake lights). Power into these 2 fuses are not switched by the ignition circuit; they are hot all the time.
There are 3 fuses together on the other half of the fuse block that should have power when the key is in the ON position. (Check both sides of each fuse BTW). If you are not getting this to happen, then likely you ignition switch itself is bad or the connections up in the column or the power is not getting to the ignition switch. You should have power to the RED wire to the ignition siwtch all the time. Is that the case?