Hard or braided lines are always a smart way to go for trans lines. Being trans fluid is so flammable you don't want any hoses slipping off or barbed fitting or holes burned through a rubber line. Being the exhaust is usually in close proximity it is a good idea.
The trans uses 1/4" npt fittings. So 1/4" npt to -6 would be a good choice. I believe I used 45 degree fittings and 45 degree hose ends to get a good compromise of tight fitting to the trans and easy of install of the lines.
The trans cooler should be a "par and plate" cooler for best performance. I tried the largest B&M Supercooler but it did not fit. Because of that reason I used two of the next smaller B&M Supercoolers hooked in series. It is slightly more surface area than their largest cooler. Worked out great.
Mike 1986 Capri street car w/ a/c, p/s & p/w
Custom built T6 80mm s400sx based kit Shaunthony's built (Twin Trouble and Anthony Fury)
9.31 @ 146 1.39 60' on drag radials @ 3735# Kurgan tuned AEM EMS
80mm 718rwhp new 88mm 921rwhp No new track times yet