Converting a heavy inline 4 OR get dual purpose?

[Geckei_kan]

Hello all, I'm new to here.

I love to go fishing to lakes. Recently I found a beautiful spot to fish but it was deep in the mountain and i had to go scratching my car's bumper and muffler.
I thought it would be nice if I have one of the adventure bikes but i can't afford any of new bikes. My budget is like $2000 or less...

So my question is should i go for a cheap old dual purpose with my low budget or convert my (old) heavy 4 cylinder to dual purpose?
I have a CB750C. I really like look of this bike but I know its too heavy to climb up hill or any hardcore off road.
But with $2000 I can do something make my bike super off roader with the look of old school... hopefully.
I know it's gonna be a pain in the ass but I know mostly what i have to do for the conversion.
I also know how heavy it is... and not only the weight... I heard that inline 4 engine is not good on off-road bcuz of traction and stuff.
Those concerns are keeping me away from tackle into this conversion. It would be nice tho because there's not many converted CB750s.

Or I should get cheap dual purpose? Only my concern is the on-road capability of dual purpose.
I was thinking to get 250cc bike but since the way to get the fishing spot there is highway too.
I don't wanna hear any of my bike screaming and shaking so much. It will be uncomfortable as well.
I thought 90-96? XT600 from Yamaha looks cool and with this engine capacity highway trip will not be bad at least. Plus, it is very rare bike in the US...

I know some of you don't give a fuck bout my day trip fishing but I'm thinking all day which i should go for.
Any idea would be appreciated. I wanna hear expert's opinion here. Because I have never tackled any hardcore off road you guys are experts for me.

Here's my bike