My car ('87 with, originally, the LG4 305) has the factory hardlines coming from the fuel tank, but they're rotten and need replacing. Should I care at all to put in more hardlines or say screw it and use braided stainless. To answer future questions, yes, it'll one day have fuel injection again.

 

Hardlines are objectively better, I would be tempted to replace them assuming stock diameter fuel line meets your power goals. Otherwise there's nothing wrong with fuel rated braided hose. Custom anything tends to be more money and more work.

 

I thought somehow this was a LG4 car?

So, the whole fuel system in it, was designed for low pressure; suction in fact, in lots of it. Not at all suitable for EFI with 50ish psi of pressure all over the place. And of course it's FUEL you'll be dealing with, which if the system allows ANY of that to leeeeeek, is DEATH. To you AND your passengers. It SUCKS for your car to burn to the ground while on a cruise on a pretty Sunday afternoon with your family aboard because of a leeeeeeeeeeeeeek. Yeah IT HAPPENS. It can happen TO YOU if you're careless.

That said though, "hard line" of practically ANY sort can withstand that easily, although the fittings at the ends may limit it somewhat. A slip-over hose "barb" such as is usually found on the end of a typical carb system fuel line for example, is fundamentally inadequate for anything in the EFI realm, NO MATTER WHAT kind of hose you slip over it.

If it was me, I'd go back with hard line of some kind, butt perhaps with short sections of stainless-braided at the ends where there's flexing and vibration. For those little short (less than 12") bits, I'd use PTFE lined hose, NOT the traditional rubber stuff, most especially it the car is parked indoors (garage) or an enclosed trailer, since it also SUCKS when buildings explode from gasoline fumes. I'd flare the ends of the hard line with 37° AN flares so that an absolute bare minimum of adapter fittings are needed.

 

Vibrant makes male -AN to female inverted flare adapters, that was easier for me because 37 degree flaring dies didn't come in my kit.

 

This is an easy question to answer. If you plan on staying stock, use stock hard lines. If you want to future proof it for performance efi setup run 6an/3/8ths hard feed and return lines. The stock LG4 used 3/8 line for a feed. The lg4 doesn't care what size return you have but a future efi w enough HP likely will. You could likely just by 2 stock replacement 3/8 lines and modify one to work w compression fittings that would adapt to stock return sizes. Use some high quality flex sections where needed.

 

If you change the tank and sending unit to a later TPI style they make drop in stainless line kits that are direct factory replacement. That's what I have, even though my car is an '87 2.8l I got all the parts for a '92 TPI 350 and they went in with no problem. This is feeding a Super Sniper 4150 eight injector and there is zero issue 3/8 feed 5/16 return with a aeromotive stealth 340 pump and fuel pressure regulator. We got braided stainless lines made up for the connections from the body to engine and that was $350, I can't even imagine how much it'd be for a set front to back.

 

My comment on the 6an/3/8 return are due to things that you may or may not notice right away. You may have issues with fuel pump life. The added resistance can cause it to run hotter. There are lots of variables. Fuel pressure and fuel requirements of the engine will play a roll. Yes, you can get away w a smaller return, I totally did. But I also got to replace a couple of fuel pumps. If you look at all the efi companies and fuel delivery companies, they recommend equal size feed and returns.
I'm aware the stock systems use the smaller return. If you're doing a stock efi, by all means use a stock fuel system. If you have plans on adding significant power and or using an aftermarket efi, use the larger line.

 

It might also be worthwhile to consider the metallurgy. "Stainless" is a broad category of materials. If you are in an area where there is sea spray, or where roads are sometimes coated with sodium- or potassium-chlorides to melt ice, you might want to be a bit more selective about the material. A little research might clarify why ocean going vessels (bathed in salt water) more often use bronze propellers and trim and not stainless.