I just got registered and now I need your help already

we just bought this...
1970 Plymouth GTX ~440/6 Pac~Auto~Fully Restored~Emerald Green/Green~
1970 Plymouth GTX
"V Code"
41,081 Original Miles
ALL Original Metal w/ No Rust on Lips
Period Correct 440/6 Pac w/ 484 Purple Cam(From 1970 Dodge R/T 6 Pac)
Build Sheet!!
Fully Restored w/ Only 1,300 Miles
Forest Green/Dark Green Interior
All Gauges Restored w/ White Lighting
2 Sets of Wheels & Tires
Awesome Sterio System w/ Amp in Trunk
With Current Owner Since 1991
Original Manifolds & OEM Spark Plugs Included
its being shipped over in the next few weeks and we want to change the transmission and brakes etc to make it more usable in europe.
It currently does a 0-60 in supersonic time but flat out its 65 mph !!!!
What mods does it need and who in New York state can do it or failing that here in UK? we would like to get it done there I think.
Many thanks
Roger