I drove through Tanzania from Mtwara to Tanga (full east coast) and then down from Rwanda to Dodoma on my way to Malawi earlier this year. I also took my motorbike across to Zanzibar.
I loved it, the drivers were courteous, not so many cyclists on the road and no major problems with pedestrians.
The police, trucks and buses didn't bother me at all.
There's obviously going to be a massive difference in terrain but if you looking for dirt tracks, sand and corrugations Tanzania's got it all.
Please take the job..
You'll love it.
I'll be back there in a couple of months, can't wait.