You don't mean dcoe48's do you? If you are keen on building an engine, first know it's not a cheap exercise.
What head do you have currently? If it's an h75 it's a low comp head.
I you want to build a decent engine with good comp I would eithe look at buying an h89 or GX head, neither cheap however both high comp with the GX head being double valve springs.
You can have the h89 head seated for double valve springs for not too much money. Otherwise you can do some porting on it with bigger valves.
As for the block you can just bore the s**t out of the block and put a nice set of flat top pistons on. You can look at lightening the flywheel and crank, and have everythig balanced.
I don't know enough about what cam degree to use however have a good look at what your driving this engine will be use for. There is no point putting in a race cam that only starts to pick up at 6-7 grand that's meant for speedway racing if it's going to be a daily driver....
Also you can prob just have the cam you already have reground by a decent machinist in your area. There is usually a cam specialist near by....
Honestly I don't really know enough with specs and what not your best to have a chat to member "bige" (Earnie) he's more than happy to chat...
As for 15 seconds 1/4 mile dunno if that's achievable with a worked a14, have a look on YouTube there is an a15 turbo ute running good times from memory... Pretty sure one of the videos is datsun 1200 ute eats gtr skyline....