The brake pipes on these rot out under the L shaped panel and in the brackets .
N/S/R is easy enough to change but the O/S/R goes over the gearbox .
If you are replaceing it with the Porsche pre made pipe then to be honest its engine out , coolant pipe plus all the other pipes dropped then replace .
If you dropping the engine then things like the AOS are a Must to replace .
I would also have a good look at the coolant pipes on the n/s chassis .. replace if needed .
If you are makeing your own pipe then just gearbox out and feed the brake pipe under the pipes .. all you are trying to achieve is to make sure the brake pipe is secure in the brackets and will not flap around possibly rubbing through over time .
You can try to do this with the gearbox in situe .. if the pipe is secure then fine .. not easy though .
You also have the option of a cut and join .. you basically cut the pipe to remove the corroded parts , flare the end and fit a joiner .
Ive done all three depending on what the customer can afford , as long as the pipe is secure and leak free then the job is a good un .