UP/down counter & shiftout interupt problem

Hi all

I'm looking for someone who can give me some advice to brainstrom about the following problem
I want to convert an icremental encoder to a 16bit/360 degrees serially shiftout output

I have pulses generated from an incremental encoder which are differential
quadrature

I convert the differential part to TTL by a 26LS32
then the quadrature TTL to UP/DOWN counter by a LS7184

So I will have a TLL negative going clk for each pulse and a second pin
show the direction UP as logic 1 or 0 as down count

Lets assume that in a proper setup routine we determine
"Zero" as xxx pulses for 0 degrees and "full span" as xxx pulses for 360 degrees

Now I want to convert to a 360 degrees format in a 16bit word
which will be shiftout to an external device
this device has a "LOAD" to start the shift register on the bus
a Clock and a data pin to clock the data out

My question is how should i handle the incomming pulses from the incremental encoder, and the incomming LOAD,CLK from the external device ? possible at the same or almost the same time
Speed is not an issue let's say pulses for 1 revolution are max 1/10 second

Shall i use hardware interupts etc ???

I never played with hardware interupts so I need some help from the PRO's

Thanks to you all