You are north of me.
The WGAL on real 51 is not built. WGAL applied for a translator on RF51, but after a power boost on RF8, they decided they did not need it. If you search the FCC for WGAL, there are no entries for channel 51.
http://transition.fcc.gov/fcc-bin/tvq?state=&call=wgal
WHTM RF 10 is going to be hard to get. Between you and the transmitter is hilly. It is multi-path hell.
The Philadelphia stations are probably out of reliable range because of the terrain between you and them. You could aim an all band antenna at Philly but don’t expect 24/7 perfect reception.
I suggest you focus on the 300ish True stations.
You are going to want separate VHF and UHF antennas.
WHTM (ABC, virtual 27, real 10) may be a bear to get. I would aim a Y10-7-13 at WHTM. To get the aim right, I would connect a balun from the Y10-7-13 to a coax directly to whichever TV has a better signal meter. Then fine tune the aim to get the best signal possible for WHTM.
WGAL on RF8 may be a problem, they have had issues with the terrain. Fortunately you have the option to use the translator on RF 49. Either the Y10-7-13 aimed for WHTM will get WGAL on 8, or you will get WGAL on RF 49. You might even get both, and have duplicate virtual channels 8.1 and 8.2. You can delete whichever is weaker.
WGCB on RF30, virtual 49 is MeTV with religious programing, infomercials, and ST:TNG added; they have MeTV in its full schedule on a sub channel. They also recently got a 3rd sub channel. So, you can either take or leave WGCB. It is a 2 edge path and it is away from the rest of your channels, if it comes in when you optimize your UHF aim for Fox, PBS, CBS, and CW, consider it a bonus.
WPMT and WLYH are your strongest channels, so them being the outliers on your UHF grouping is a bit of a blessing. I would aim a db8e half way between them which nicely corresponds to multiple stations at 310 True. None of your UHF 300ish-degree stations need extreme gain, so you can probably use any well-built 8 bay antenna instead of the db8e if you need something less expensive. An 8 bay is recommended in your case because there is some spread to your stations so a high gain yagi might be too directional, but multipath is a concern, so a 4 bay would not be directional enough.
TV fool predicts LOS paths for a bunch of stations, but the terrain around the Harrisburg, Lancaster and York transmitters seems to breed multipath which is why the big guns (db8e and Y10-7-13) are recommended.
I have used a RCA TVPRAMP1R with an 8 bay antenna and my strongest signal being -27.4 dBm without notable overload problems. For a 2 way split you probably don’t need a preamp except for WHTM. However since the TVPRAMP1R has a UHF VHF joiner built in and WHTM really makes your situation a separate antenna case, I think it is fair to recommend a TVPRAMP1R.