Hello there,
I agree that there are a number of problems here.
The 741 severely limits the usable input frequency to be measured. Start with just a gate for digital signals and add a high speed op amp for lower level signals perhaps later on once everything else is working right.
Also, is the "TR" of the 555 actually an input? I would think the output that the gate signal should come from the output of the 555. Also, depending on the accuracy, the 555 is not the best choice for a gate signal oscillator you probably want to use a crystal oscillator for that, but yes that can come later on once you get everything else working properly.
I like the idea of the little delay circuit to delay the latching pulse. That gives the counters time to settle.
As Eric says, you should be using the LS192 counters not the LS193 because you want a BCD output not a binary output. However, if you are going to bother using synchronous counters then you might as well also CONNECT them as synchronous counters. The way you have the connected now looks like you have them connected as asynchronous counters which is not as good because the last bit takes N delay periods to flip, where N is the number of flip flops and this delay can be significant. Connecting them as synchronous counters means all the output bits change at very nearly the same time which means the latches can catch the count faster (less delay required). They dont function as perfectly synchronous counters this way, but are much better than ripple carry counters which do require that N bit delay. With the synchronous connections the delay is only an N package delay.