its is ok to change MXR dist+ diodes (i think is 1n270) for 1N914... maybe not a good idea? let me know

Quite common in this ckt...

try cahnging only one of them with a 1n4001

i don't think it'll blow anything up, if thats what your asking.  Try it, and see what kinda sound you like.  maybe even put a switch to switch between symetrical and asymetrical clipping or something.

The 1n270 is germanium similar to 1n34a. I like Ansil's suggestion replacing only one of them with a 1n4001,2,3,4 etc whatever you have lying around or a 1n914 or 1n4148 silicon (sounds good). Mix and match, try sockets - some people like leds - have fun!