If you only have 1 skimmer and 1 return line, your head will be quite high with a full rate 1 HP pump. I estimate over 70 ft of head which is mainly due to the 1.5" 75 ft of suction pipe.

The maximum recommended GPM for 1.5" pipe is about 42 GPM. If you go with a 3/4 HP, the head will drop to 60' @ 57 GPM. At 1/2 HP, the head will drop to 47' @ 50 GPM. These are only approximate since it depends on the pump type.

Here is a web site to help with pump sizing:

http://www.poolplaza.com/pool-pump-sizing-2.shtml