1999 speedo in a 98?
 

Can a 1998 softail be rewired so that a 1999 Speedometer will work on the bike?

Do you have the bleed-out in the old LCD odometer?
The black spots in the LCD display of the odometer?
There is a sticker on the backside of your old speedometer. Look at that sticker and look at the part number.
Then go online to cross check updated number.
In 1998 there was a problem with bleed-outs/black leak marks on the odometer.
The replacement unit and any other unit will require an adapter plug.
If you look at your 1998 speedometer you will notice it is NOT a plug and play unit and changing to anything else will require the splicing of about 12 wires to that adapter plug. Again this is not a plug and play situation. The adapter plug is about $50.
You will need a connector plug for the replacement unit in order to have "leads".
Review this link for posi-lock connectors in order to simplify the situation and remember to stagger connections. http://www.webbikeworld.com/sale/pos...s-for-sale.htm The mileage record is in the unit NOT the ECM for that vintage so the odometer will not match actual miles unless a mileage correction is done by a licensed facility. If you still need information just go to the harley website and look at speedometer installation instructions in PDF for special units or look at PDF instructions of any popular after market speedometer unit.
So to answer your question: yes

Most of the characters that make up the numbers don't work so I can't read the mileage anyways