**Disclaimer - Electrical stuff confuses me **
When I swapped a 3FE into an FJ60 I used the FJ62 wiring harness. In plugging the round headlights into the sockets which had had the rectangular bulbs, what I discovered was that the high and low operations of the bulb were opposite, ie. high at the switch gave low at the bulb. I then had to sort this out, and what I did not know was that Toyota uses a single 12 v wire for the lights and a ground is switched between the high and low settings (see above disclaimer).
I will present the headlight wiring scheme as I understand it (and try to have it verified). The following diagrams will be of a view of the rear of the lamp.
FJ60
low
-----
| |
| |
high comm
FJ62/H4 (I am assuming the FJ62 pattern = that of an H4 bulb)
High
____
| |
| |
low common
Therefore, to run round 7" headlights with an FJ62 wiring harness, you would need to swap around the wiring to the appropriate positions.
Within the past year I've gone to IPF lights with Hella H4 80/100 watt bulbs using a Wayne Tangen auxiliary wiring harness
http://www.ih8mud.com/tech/headlightharness.php and
http://www.ih8mud.com/tech/headlightharness/diagram.pdf.
The improvement in lighting has been dramatic. I followed Wayne's instructions and built my harness knowing that I would have deal with a minor deviation in how it was plugged into the stock harness.
An option to cutting and splicing the stock wiring would be to make pigtails to connect between the stock plug and the headlight. In that manner you could easily swap wires around to confirm that you have things properly wired.
The mulitmeter is your friend.
And I will repeat **Disclaimer - Electrical stuff confuses me **