Is using a 4x4 bolted to the face of 2x12 enough?

I am working on a project that has three 2×12’s supporting a load of 12,000 lbs. similar, but not exactly, to how joists support a house.

The 2×12’s are supporting about 6,000 lbs. on each end.

The three 2×12’s are:
a) Each cut to 90in.

b) The load takes up 24in. from each end of the 2×12’s leaving 42in. of free space in between.

c) The three 2×12’s are spaced parallel to each other, with one 2×12 being 24in. in front of the other.

d) The 6,000lb. (On each side) load is laying on a thick wooden plank (on each end) that is perpendicular to the three 2×12’s.

e) The two thick wooden planks on each end of 2×12’s (mentioned in “d”) is securely fastened to the 1.5in. part of the 2×12’s, as well as having blocking and other bolted wooden members that leaves (as stated in “b”) 42 in. Of free space in between.

f) The three 2×12’s are only 12in. off the ground.

Everything is stable and strong without any issues except for one.

I need to lift this so that it is 14in. off the ground (lifting it 2 in. in total).

Removing the load; as well as dissembling is not an option.

This will have to be lifted with the three 2×12’s and everything above (including load) remaining intact.

My best option is to lift (with a hydraulic jack) the front most 2×12 to 14in. and then lift the back most 2×12 to 14in.
-I’ve done this before with no problems.

The only problem, that I have now, is that directly under the 2×12 is things that I can not remove and is not strong enough jack it from.

The saddle of the jack is 2in.
All wood is Douglas Fir #2 or better.

My plan is to bolt a 4×4 cut to 42in. (to fit in the free space mentioned in “b” and to better distribute the force of the jack).

This 4×4 will be bolted (3 bolts spaced almost equally apart) to the outward face of the 11.25in. part of the front most and back most 2×12’s.

Questions:

1. Do you think is strong enough to support the load plus force of the jack or do you think it will just rip the 4×4 off of the 2×12; while also destroying the face of the 2×12’s?

2. Do you think maybe adding a 4×4 on the inward faces of the 2×12’s (these will not have the jack touch it) will provide any more strength to make this process acceptable?