Creating an Overworld portal to a specific location in the Nether

Solution 1:

The short answer is no. When You enter the a portal from the nether, on your way to the overworld, Minecraft calculates the primary portal coordinates with this generalized equation:

{X, Y, Z} → {floor(X) × 8, Y, floor(Z) × 8}

The game then checks for an active portal in a 128 block radius around that location. Given your nether portal coordinates:

X: -70; Y: 72; Z: -139

Your overworld portal must be within the following horizontal bounds:

X = -688, -432
Z = -1240, -984

Remember, any overworld portals within 1024 blocks of each other will link to the same nether portal, because 1024 blocks in the overworld = 128 blocks in the Nether, and the game checks for portals in a radius of 128 blocks.

If you build a new nether portal at the blaze farm and destroy your old portal, your main base portal will probably link up to your blaze farm. However, when you attempt to go back to the overworld, Minecraft will look for a portal within the above bounds and create a new one if it doesn't find one.

Your best option is probably to build a rail line from your current portal to the blaze farm. Ghasts can destroy any block with a blast resistance below 20.17, but they won't shoot at you without a line of sight, so you can make an inexpensive safety-tunnel around your rail line with pure Netherrack.

You can also build a more scenic tunnel with stone, glass, leaves, fences, etc, since Ghasts cannot "see" through transparent blocks.

Solution 2:

One thing you can utilize is "hidden" or at least generally "off/on" portals. It takes a bit of creativity to get it working just the right way, but it can totally produce results and can allow you to have multiple portals in a small area all leading to different things.

See my answer here for an example of how I used it in a functional situation, as well as additional info related to linking portals, in the context of that post. In the context of yours here is the relevant info copied over:

In one of my worlds (Xbox 360) I have an underground pyramid. At the top of the pyramid is a portal which anyone will find on their way down from the overworld. If they enter this portal they go to the nether hub, if they enter the portal in the nether hub they return to this top portal.

I have this or a similar design (one of Mumbo's probably) nearby in my pyramid: (linked below)

This hidden portal actually turns /off/ as you teleport. It takes you to a secret room BELOW the nether hub portal. Taking the portal out of there...well the portal you took to get in is hidden/turned off so it "doesn't exist" and the game will want to create a new exit portal for me, but I purposefully placed it close enough to the "normal" portal that instead of creating a new portal close to where the "hidden" one is it just sends you to the former.

• Different ratios for portal linking depending on world size (I believe this only affects console versions of the game as the PC is default to "unlimited" map size with the 8-1 ratio): http://www.gamefaqs.com/boards/728000-minecraft-playstation-4-edition/70175025

• Some linking concepts (try other videos; no one seems to cover ALL the caveats):

• Something I used in conjunction with creative linking to build "hidden" transportation systems: