if you put synthetic fluid in it drain it out and use reg crappy walmart gear oil. itll shift better. synthetic usually doesnt allow the synchros to grab. sounds like the problem your having honestly. ive dealt with this on r154's many times.

as for the speedo issue, you need to find out what rear diff gears you have and get the speedo gears to match for the trans. they are kind of a pita to change.