hi,
THe 74LS193 is binary counter so you would use the Qc output, for a count of 8, of the first LS193 to drive the second LS193.
For a count of 5 you would need to detect when the second LS193 has counted to 6 say, thats Qb and Qc outputs, when this count of 6 is detected it drives the clear pin on the second LS193.
An 'AND' gate would be used to detect Qb and Qc.
If the the count rate is low, then a couple of signal diodes and a resistor could make the 'AND' gate.
As the the LS193 is a synchronous counter there are a number of ways to detect and restart for a count of 5.
Do you follow this OK.?