That is almost correct, 53-58 is the require pressure per GM Swap guide. But you are better off trying to stay as close as possible to 58 psi or more if you start mod'ing.
No you don't have to use a Intank pump, but you need to reseach the pro and con of both internal and external tanks. External are noise and sometime don't have a very long life. Internal are cooled by being submerged in the fuel and keep cool and will last long as any OEM setup. Noise is blocked by being submerged in the fuel in in the tank.
Another question you should be asking if going internal, is what Fuel Tank or which way to mod the tank.
a) There are Aftermarket tanks that have internal pumps all ready added, some will run up to $1200.00. Search on A-Body tank, there is a aftermarket replacement w/intank pump for a few hundred dollars.
There is a Thread on it.
b) Many have also used the
Tank.INC intank setup.
c) Some will sump there current tank with a
Competition Engineering Sump and use a external pump.
d) If your doing your A-Body, a B-Body Impala/Buick (94-96) tank can be swapped in.
ls1 what fuel pump 
