[BYprodriver]

IF you are Positive the threads are nice & clean & lubed in the case & the trans bolts.
Make sure the weight of the engine & trans are not working against your progress & you are perfectly lined up. Begin to thread bolts into their proper place & evenly thread them in making sure you are pulling the trans toward the engine, Not pulling the threads out of the case. That is easy to do. Having someone press down on the clutch pedal helps ONLY IF the slave cylinder pushrod is contacting the throwout bearing lever. It looks like it should be in far enough in your pic, But if the slave pushrod is not centered properly it will blowout the slave cylinder. To insure the input shaft is in the clutch splines properly turn the output flange.

PS. Don't use the nut & bolt fastener @ 5:00 position until trans is fully in place with no gap at the bellhousing! (This applys to 6-speeds) not sure about 5-speed.