Mohit, why are you using two discontinued chips?. I agree with Greg that using the '245 is a pain in your largest muscle. If the two chips have OE (output enable) pins, you do not need the '245 and will avoid a lot of problems. I have over time inherited a few designs using the '245 and have always had to "squeek" solutions in, in one instance the only solution - and believe I hate this - was to mix a 74 chip of a different family in to get the timing right. If you REALLY, ABSOLUTELY, DESPERATELY need to include the '245 and 2 obsolete chips, try first the very fastest '245 you acn get and make sure that your address decode logic for the chip selects is ultrafast as well.
Sorry about the discouragement.

Erik Malund